Does The Ventral Root And Dorsal Root Makeup Spinal Nerves

BIO 301
Human Physiology

Neurons & the Nervous System - Part 2

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The Human Nervous System consists of the Central Nervous System & the Peripheral Nervous System.

Central Nervous System:

1 - Brain

ii - Spinal cord

Peripheral Nervous Organization:

one - Cranial nerves (12 pair) & their branches

2 - Spinal nerves (31 pair) & their branches

Divisions of the nervous system

Central Nervous System

Source: training.seer.cancer.gov

Source: http://postal service.med.upenn.edu/~hessd/Lesson3.htm

Divisions of Peripheral Nervous System -

1 - Somatic - supplies & receives fibers (neurons) to & from the skin, skeletal muscles, joints, & tendons

Used with permission of John Kimball

2 - Visceral - supplies & receives fibers to & from smooth muscle, cardiac musculus, and glands. The visceral motor fibers (those supplying smooth musculus, cardiac musculus, & glands) brand up the Autonomic Nervous System. The ANS has ii divisions:
• Parasympathetic division - important for control of 'normal' body functions, e.g., normal operation of digestive system
• Sympathetic division - as well called the 'fight or flying' division; important in helping us cope with stress

Source: http://faculty.washington.edu/chudler/nsdivide.html

Divisions of the Human Brain:

one - Myelencephalon, which includes the medulla

ii - Metencephalon, which includes the pons and cerebellum

iii - Mesencephalon, which includes the midbrain (tectum and tegmentum)

four - Diencephalon, which includes the thalamus and hypothalamus

5 - Telencephalon, which includes the cerebrum (cognitive cortex, basal ganglia, & medullary trunk)

Used with permission of John Due west. Kimball

Man encephalon (coronal department). The divisions of the brain include the (1) cerebrum, (2) thalamus, (three) midbrain,
(iv) pons, and (5) medulla oblongata. (six) is the height of the spinal cord (Source: Wikipedia).

Structures of the Brain:

Medulla (too called medulla oblongata) -

1 - continuous with spinal cord

2 - contains ascending & descending tracts that communicate between the spinal cord & diverse parts of the brain

3 - contains 3 vital centers:

• cardioinhibitory center, which regulates center rate
• respiratory eye, which regulates the bones rhythm of breathing
• vasomoter center, which regulates the bore of blood vessels
4 - origin of five cranial nerves (VIII or vestibulocochlear, 9 or glossopharyngeal, 10 or vagus, XI or accompaniment, & XII or hypoglossal)

Pons -

1 - Span connecting spinal string w/ brain & parts of brain w/ each other

2 - Origin of four cranial fretfulness (V or trigeminal, VI or abducens, VII or facial, & VIII or vestibulocochlear)

3 - contains pneumotaxic center (a respiratory center)

The encephalon stalk is the region between the diencephalon (thalamus and hypothalamus) and the spinal cord. It consists of three parts: midbrain, pons, and medulla oblongata. The midbrain is the most superior portion of the brain stem. The pons is the bulging middle portion of the brain stalk. This region primarily consists of nerve fibers that form conduction tracts between the higher brain centers and spinal cord. The medulla oblongata, or simply medulla, extends inferiorly from the pons. It is continuous with the spinal cord at the foramen magnum. All the ascending (sensory) and descending (motor) nerve fibers connecting the brain and spinal cord laissez passer through the medulla (Source: training.seer.cancer.gov).

Midbrain -

1 - Corpora quadrigemina - visual reflexes & relay center for auditory information.Two pairs of rounded knobs on the upper surface of the midbrain mark the location of iv nuclei, which are called collectively the "corpora quadrigemina." These masses contain the centers for certain visual reflexes, such as those responsible for moving the eyes to view something as the head is turned. They also contain the hearing reflex centers that operate when it is necessary to move the head so that sounds tin can be heard ameliorate.

2 - Cognitive peduncles - ascending & descending fiber tracts

3 - Origin of two cranial nerves (3 or oculomotor & IV or trochlear)

1- posterior medullary velum, 2 - choroid plexus, three - cisterna cerebellodellaris of subarachnoid cavity, 4 - central canal,
5 - corpora quadrigemina , half-dozen - cognitive peduncle, 7 - anterior medullary, 8 - ependymal lining of ventricle, & ix - cisterna pontis of subarachnoid cavity
(Source: Wikipedia).

Brain stem

Brainstem

Thalamus -

1 - Relay station for nearly all sensory impulses (except olfaction)

Source: http://songweaver.com/brain/alphabetize.html

Thalamus

Hypothalamus -

1 - Command of Autonomic Nervous System

ii - Reception of sensory impulses from viscera

3 - Intermediary between nervous arrangement & endocrine system

four - Control of torso temperature

5 - Regulation of food intake

half dozen - Thirst center

vii - Part of limbic system (emotions such as rage and assailment)

8 - Part of reticular formation

Functions of the hypothalamus

Reticular formation -

ane - portions located in the spinal cord, medulla, pons, midbrain, & hypothalamus

ii - needed for arousal from slumber & to maintain consciousness

The ascending reticular activation organization. During periods of wakefulness, impulses from the brainstem activate neurons in the thalamus that are crucial for transmitting information to the cerebral cortex. Impulses also travel to the hypothalamus and throughout the cognitive cortex. A primal switch in the hypothalamus (SCN, or suprachiasmic nucleus) that serves equally the brain's 'chief clock' shuts off this arousal system during sleep (Figure from: Mignot et al. 2002).

Reticular germination

Cerebellum -

1 - functions in coordination, maintenance of posture, & residual

Structures of the brain

Cerebrum -

1 - largest portion of the human being encephalon

2 - consists of 2 hemispheres divided by a fissure

Source: http://faculty.washington.edu/chudler/split.html

three - includes cerebral cortex, medullary body, & basal ganglia:

• Cortex:
• outer ii - 4 mm of the cerebrum
• consists of gray matter (cell bodies & synapses; no myelin)

• 'folded', with upfolded areas chosen gyri & depressions or grooves called sulci
• consists of four primary lobes

Source: http://kinesthesia.washington.edu/chudler/lobe.html

• functional areas include motor areas (initiate impulses that will cause contraction of skeletal muscles) (see A Map of the Motor Cortex), sensory areas (receive sensory impulses from throughout the body), and clan areas (for analysis)

Source: http://faculty.washington.edu/chudler/functional.html

'Forward' (a) and 'inverse' (b) model command systems for movement. According to 'instructions' from the premotor cortex (P), an area in the motor cortex (controller, or CT) sends impulses to the controlled object (CO; a body part). The visual cortex (VC) mediates feedback from the trunk part to the motor cortex. The dashed arrow indicates that the body part is copied equally an 'internal model' in the cerebellum. In the forward-model control system, control of the trunk part (CO) past the motor cortex (CT) can be precisely performed by referring to the internal feedback. In the changed-model command arrangement, feedback command by the motor cortex (CT) is replaced past the inverse model itself (Ito 2008).

Sensory cortex

Motor cortex

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The charge per unit of change in cortical thickness in children and teens of varying intelligence. Positive values indicate increasing cortical thickness, negative values indicate cortical thinning. The betoken of intersection on the ten axis (0) represents the age of maximum cortical thickness (five.six yr for average, 8.five yr for high, and eleven.2 twelvemonth for the superior intelligence grouping).

Cortex matures faster in youth with superior IQs -- Children and teens with superior IQ's are distinguished by how fast the thinking part of their brains thickens and thins as they abound up. Magnetic resonance imaging (MRI) scans showed that their brain's outer mantle, or cortex, thickens more than rapidly during babyhood, reaching its superlative subsequently than in their peers — possibly reflecting a longer developmental window for loftier-level thinking circuitry. Information technology also thins faster during the late teens, likely due to the withering of unused neural connections as the brain streamlines its operations. Although near previous MRI studies of brain development compared information from different children at different ages, Shaw et al. (2006) controlled for individual variation in brain construction past following the same 307 children and teens, ages v-19, as they grew up. Most were scanned two or more times at two-year intervals. The resulting scans were divided into iii equal groups and analyzed based on IQ test scores: superior (121-145), high (109-120), and average (83-108). The researchers plant that the relationship between cortex thickness and IQ varied with historic period, particularly in the prefrontal cortex, seat of abstract reasoning, planning, and other "executive" functions. The smartest 7-year-olds tended to start out with a relatively thinner cortex that thickened rapidly, peaking past historic period 11 or 12 before thinning. In their peers with average IQ, an initially thicker cortex peaked past age 8, with gradual thinning thereafter. Those in the high range showed an intermediate trajectory (see below). Although the cortex was thinning in all groups past the teen years, the superior group showed the highest rates of modify. "Erudite children are not cleverer solely by virtue of having more or less grey affair at any i age," explained co-author J. Rapoport. "Rather, IQ is related to the dynamics of cortex maturation." The observed differences are consequent with findings from functional magnetic resonance imaging, showing that levels of activation in prefrontal areas correlates with IQ, note the researchers. They suggest that the prolonged thickening of prefrontal cortex in children with superior IQs might reflect an "extended critical menstruum for development of high-level cognitive circuits." Although it'southward non known for certain what underlies the thinning phase, evidence suggests it likely reflects "utilize-information technology-or-lose-it" pruning of brain cells, neurons, and their connections equally the encephalon matures and becomes more efficient during the teen years. "People with very active minds tend to have a very active cortex," said co-author P. Shaw.

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• Medullary body:
• the 'white matter' of the cerebrum; consists of myelinated axons
• types of axons include:
• commissural fibers - acquit impulses between cognitive hemispheres (and class the corpus callosum)

Source: http://faculty.washington.edu/chudler/sagittal.html

• projection fibers - conduct impulses in & out of the cerebral hemispheres
• clan fibers - conduct impulses within hemispheres
• Basal ganglia:
• masses of gray affair in each cerebral hemisphere
• important in command of voluntary muscle movements

Basal ganglia

Limbic System -

one - consists of a group of nuclei + fiber tracts

ii - located in role in cerebral cortex, thalamus, & hypothalamus

3 - Functions:

• aggression
• fear
• feeding
• sex (regulation of sexual bulldoze & sexual behavior)

Limbic system

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Emotion and retention

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Spinal cord

The spinal cord extends from the skull (foramen magnum) to the beginning lumbar vertebra. Like the encephalon, the spinal cord consists of greyness matter and white matter. The grayness matter (jail cell bodies & synapses) of the string is located centrally & is surrounded by white thing (myelinated axons). The white thing of the spinal string consists of ascending and descending cobweb tracts, with the ascending tracts transmitting sensory data (from receptors in the skin, skeletal muscles, tendons, joints, & various visceral receptors) and the descending tracts transmitting motor data (to skeletal muscles, smooth muscle, cardiac musculus, & glands). The spinal cord is also responsible for spinal reflexes.

http://en.wikipedia.org/wiki/Image:Medulla_spinalis_-_tracts_-_English.svg

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Reflex- rapid (and unconscious) response to changes in the internal or external environment needed to maintain homeostasis

Reflex arc - the neural pathway over which impulses travel during a reflex. The components of a reflex arc include:

ane - receptor - responds to the stimulus
2 - afferent pathway (sensory neuron) - transmits impulse into the spinal cord
3 - Central Nervous System - the spinal cord processes information
4 - efferent pathway (motor neuron) - transmits impulse out of spinal cord
v- effector - a muscle or gland that receives the impulse from the motor neuron & carries out the desired response

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Reflex arc

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Spinal Fretfulness:

Source: http://nanonline.org/nandistance/nanneuro/modules/cranial/cranial.html

In that location are 31 pair of spinal nerves & each has a dorsal root and a ventral root. The dorsal root is sensory (all neurons deport impulses into the spinal string) while the ventral root is motor (all neurons conduct impulses out of the spinal string). The dorsal root has a ganglion that contains the prison cell bodies of the sensory neurons that pass through the dorsal root. Each spinal nerve includes numerous sensory, or afferent, & motor, or efferent, neurons. Some of these neurons are classified as somatic, and these neurons conduct impulses to or from 'somatic' structures (skin, skeletal muscles, tendons, & joints). Other neurons are 'visceral', and these conduct impulses to or from 'visceral' structures (smooth muscle, cardiac muscle, and glands). Thus, all neurons in spinal fretfulness (& the peripheral nervous system) can be placed in one of four categories:

• Somatic afferent
• Somatic efferent
• Visceral afferent
• Visceral efferent

Somatic afferent neurons are sensory neurons that conduct impulses initiated in receptors in the pare, skeletal muscles, tendons, & joints. Receptors in the skin are responsible for sensing such things as affect, temperature, pressure level, & pain and are called exteroceptors. Receptors in the skeletal muscles, tendons, & joints provide data nigh body position & movement and are called proprioceptors. Somatic afferent neurons are unipolar neurons that enter the spinal cord through the dorsal root & their cell bodies are located in the dorsal root ganglia.

Somatic efferent neurons are motor neurons that comport impulses from the spinal cord to skeletal muscles. These neurons are multipolar neurons, with cell bodies located in the gray matter of the spinal string. Somatic efferent neurons leave the spinal cord through the ventral root of spinal nerves.

Visceral afferent neurons are sensory neurons that conduct impulses initiated in receptors in smooth muscle & cardiac muscle. These neurons are collectively referred to as enteroceptors or visceroceptors. Visceral afferent neurons are unipolar neurons that enter the spinal cord through the dorsal root & their cell bodies are located in the dorsal root ganglia.

Visceral efferent neurons are motor neurons that bear impulses to smooth muscle, cardiac musculus, & glands. These neurons make up the Autonomic Nervous System. Some visceral efferent neurons begin in the brain; others in the spinal cord. Because nosotros're focusing on spinal fretfulness right now, nosotros'll focus on those that brainstorm in the spinal cord. It ever takes two visceral efferent neurons to behave an impulse from the spinal string (or brain, in some cases) to a muscle or gland:

• Visceral efferent 1 (as well called the preganglionic neuron) is a multipolar neuron that begins in the grey affair of the spinal cord, which is where its prison cell body is located. This neuron leaves the string through the ventral root of a spinal nerve, leaves the spinal nerve via a structure called the white ramus, then ends in an autonomic ganglion (either sympathetic or parasympathetic). In the ganglion, the visceral efferent i neuron synapses with a visceral efferent 2 neuron.
• Visceral efferent 2 (also chosen the postganglionic neuron) is likewise a multipolar neuron and information technology begins in the sympathetic ganglion (which is where its cell body is located). Visceral efferent two neurons may exit the ganglion through the grayness ramus, so continue to some visceral construction (smooth muscle, cardiac muscle, or gland).

Source: http://world wide web.mmi.mcgill.ca/Unit2/Mandl/lect20autonomicnervoussystem.htm

The 4 types of peripheral neurons: somatic afferent (top right), somatic efferent (bottom correct),
visceral afferent (top left), and visceral efferent (bottom left).

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Autonomic Nervous Organisation:

i - entirely motor (consisting of the visceral efferent fibers)

2 - has two divisions: sympathetic & parasympathetic

• sympathetic neurons get out the central nervous system through spinal nerves in the thoracic & lumbar regions of the spinal cord
• parasympathetic neurons leave the central nervous organisation through cranial nerves plus spinal nerves in the sacral region of the spinal cord

Used with permission of John W. Kimball

Autonomic Nervous Arrangement - control of involuntary muscle

3 - impulses always travel along two neurons: preganglionic & postganglionic

4 - Chemical transmitters - all autonomic neurons are either cholinergic or adrenergic

• cholinergic neurons - use acetylcholine as a neurotransmitter
• includes all preganglionic neurons (both sympathetic & parasympathetic divisions), all parasympathetic postganglionic neurons, plus the sympathetic postganglionic neurons that supply the sweat glands
• adrenergic neurons - used norepinephrine (besides called noradrenalin) as a neurotransmitter
• includes all postganglionic sympathetic neurons (except those that go to the sweat glands)

Fight-or-flight response

5 - Functions of the Autonomic Nervous System:

• sympathetic division - prepares the trunk for strenuous physical activity in stressful situations. This response is ofttimes referred to as the 'fight-or-flight' response because the sympathetic segmentation prepares the torso to fight confronting or abscond from a threat.
• parasympathetic division - regulates important body functions such as digestion & 'slows down' the trunk after a 'flight-or-flight' response ('rest & digest')

6 - Control of Autonomic Nervous System - master command heart is the hypothalamus

Source: http://www.mmi.mcgill.ca/Unit2/Mandl/lect20autonomicnervoussystem.htm

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Back to Neurons & the Nervous System I

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Related links:

Evolution of Transmembrane Resting Potential

The Physical Factors Behind the Action Potential

Nerve Activeness Potentials

Saltatory Conduction of Action Potentials

Neurons: Our Internal Milky way

Synaptic Manual

The Autonomic Nervous Organization

The Nervous System

Explore the Brain and Spinal Cord

The Animated Brain

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Literature cited:

Ito, K. 2008. Internal-model control systems for voluntary motion and mental action. Nature Reviews Neuroscience ix: 304-313.

Mignot, E., South. Taheri, and Southward. Nishino. 2002. Sleeping with the hypothalamus: emerging therapeutic targets for slumber disorders. Nature Neuroscience five: 1071-1075.

Shaw, P., D. Greenstein, J. Lerch, L. Clasen, R. Lenroot, North. Gogtay, A. Evans, J. Rapoport and J. Giedd. 2006. Intellectual ability and cortical development in children and adolescents. Nature 440: 676-679.

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Back to BIO 301 syllabus

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Source: http://people.eku.edu/ritchisong/301notes2b.html

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