Entails anatomy and physiology of the nervous system

1. ANATOMY AND PHYSIOLOGY OF
THE NERVOUS SYSTEM

2. • The nervous system has approximately 10 million sensory neurons
that send information about the internal and external environment to
the brain and 500,000 motor neurons that control the muscles and
glands.

4. FUNCTION OF NERVOUS SYSTEM
• Sensory function
-sensory receptors gather information
-information is carried to the CNS
• Intergrative function
-sensory information used to create;
• Sensations
• Memory
• Thoughts
• Decisions

5. • Motor functions
-decisions are acted upon
Impulses are carried to effectors

7. • The nervous system is a highly complex part of an animal that
coordinates its functions and sensory information by transmitting
signal to and from different parts of its body.

16. • The brain accounts for approximately 2% of the total body weight; it
weighs approximately 1400 g in an average young adult. In elderly,
the average brain weighs approximately 1200 g.

18. CORPUS CALLOUSUM
• It’s a bridge of nerve tissue that connects the left and right cerebral
hemispheres.
• It serves as the main communication pathway or crossover station for
neural messages between the two cerebral hemispheres.
• It comprises over 200 million nerve fibres.
• Information transferred includes sensation, memory, and learned
discrimination.
• Right-handed and some left handed people have cerebral dominance on
the left side of the brain for verbal, linguistic, arithmetical, calculating, and
analytic functions.
• The non-dominant hemisphere is responsible for geometric, spatial, visual
pattern, and musical functions.

25. Functions of basal ganglia
• Control of voluntary motor activity.
• Control of reflex muscular activity.
• Control of muscle tone.
• Role in arousal mechanism.

26. Thalamus
• Lies on either side of the third ventricle.
• Acts primarily as a relay station for all sensation except smell.
• All memory sensation and pain impulses also pass through this
section of the brain.

27. Hypothalamus
• Located anterior and inferior to the thalamus.
• Lies immediately beneath and lateral to the lower portion of the wall of the
third ventricle.
• It includes the optic chiasm (the point at which the optic tracts cross) and
the mamillary bodies (involved in olfactory reflexes and emotional
response to odors).
• The infundibulum of the hypothalamus connects it to the posterior
pituitary gland.
• Plays an important role in the endocrine system because it regulates the
pituitary secretion of hormones that influence metabolism, reproduction,
stress response, and urine production.

28. • Maintain fluid balance
• Maintains temperature regulation by promoting vasoconstriction or
vasodilation.
• Site of the hunger center and is involved in appetite control.
• Centers for regulating the sleep-wake cycle, blood pressure,
aggressive and sexual behavior, and emotional responses (i.e.,
blushing, rage, depression, panic, and fear)
• Controls and regulates the autonomic nervous system.

31. • Nerve fibers from all portions of the cortex converge in each
hemisphere and exit in the form of tight bundle of nerve fibers known
as internal capsule.
• Having entered the pons and the medulla, each bundle crosses to the
corresponding bundle from the opposite side.

34. Midbrain
• Connects the pons and the cerebellum with the cerebral
hemispheres.
• It contains sensory and motor pathways and serves as the center for
auditory and visual reflexes.
• Cranial nerves III and IV originate in the midbrain.

35. Pons
• Is situated in front of the cerebellum between the midbrain and the
medulla and is a bridge between the two halves of the cerebellum,
and between the medulla and the cerebrum.
• Cranial nerves V to VIII connect to the brain in the pons.
• The pons contains motor and sensory pathways.
• Portions of the pons also control the heart, respiratory, and blood
pressure.

36. Medulla oblangata
• Contains motor fibers from the brain to the spinal cord and sensory
fibers from the spinal cord to the brain.
• Most of these fibers cross, or decussate, at this level.
• Cranial nerves IX through XII connect to the brain in the medulla.

37. Cerebellum
• Separated from the cerebral hemispheres by a fold of dura mater, the
tentorium cerebelli.
• The cerebellum has both excitatory and inhibitory actions and is
largely responsible for coordination of movement.
• It also controls fine movement, balance, position sense (awareness of
where each of the body is), and integration of sensory input.

41. Dura mater
• It is the outer most layer and covers the brain and spinal cord.
• It is tough, thick, inelastic, fibrous, and gray.
• There are four extensions of the dura:
i. The falx cerebri, which separates the two hemispheres in a
longitudinal plane.
ii. The tentorium, which is an infolding of the dura that form a tough
membranous shelf’
iii. The falx cerebelli, which is between the two lateral lobes of the
cerebellum.
iv. The diaphragm sellae, which provides a “roof” for the sella turcica.

43. Arachnoid
• It is the middle membrane; an extremely thin, delicate membrane
that closely resembles a spider web.
• It appears white because it has no blood supply.
• The arachnoid layer contains the choroid plexus, which is responsible
for the production of cerebrospinal fluid (CSF).
• This membrane has a unique finger like projections, arachnoid villi,
that absorbs CSF.
• In the normal adult, approximately 500 ml of CSF is produced each
day but 125 to 150 ml is absorbed by the villi.

45. • When the blood enters the system (from trauma or haemorrhagic
stroke), the villi become obstructed and hydrocephalus (increased
size of ventricles) may result.

46. Pia mater
• It is the innermost membrane; a thin, transparent layer that closely to
brain and extends inti every fold of brain`s surface.

49. • The ventricular and subarachnoid system contains approximately 125 to
150 ml of fluid, while 15 to 25 ml of CSF is located in each lateral ventricle.
• The composition of CSF is similar to other exracellular fluid (such as blood
plasma), but the concentrations of the various constituents are different.
• The analysis and laboratory report of CSF usually contains information on
color, specific gravity, protein count, white blood cell count, glucose, and
other electrolyte levels; it may also be tested for immunoglobulins or
lactate.
• Normal CFS contains a minimal number of white blood cells and red blood
cells.

50. Cerebral circulation
• It receives approximately 15% of the cardiac output.
• The brain dos not store nutrients and has a high metabolic demand
that requires the high blood flow.
• In contrast to other organs that may tolerate decreases in blood flow
because of their adequate collateral circulation, the brain lacks
additional collateral blood flow, which may result in irreversible tissue
damage when blood flow is occluded for even short period of time.

54. Blood- Brain Barrier
• .The CNS is inaccessible to many substances that circulate in the blood
plasma(eg dyes, medications and antibiotics).
• After being injected into the blood, many substances cannot reach
the neurons of the CNS because of the blood-brain barrier.
• This barrier is formed by the endothelial cells of the brain capillaries,
which form continuous tight junctions ,creating a barrier to
macromolecules and many compounds.

55. • All substances entering the CSF must filter through the capillary
endothelial cells and astrocytes.
• Often altered by trauma, cerebral oedema and cerebral
hypoxemia,the blood- brain barrier has implications in the treatment
and selection of medication for CNS disorders as well as serving a
protective function.

64. THE PERIPHERAL NERVOUS SYSTEM
• It includes-the cranial nerves
-The spinal nerves
-The autonomic nervous system

68. AUTONOMIC NERVOUS SYSTEM
• It regulates the activities of internal organs such as the heart,
lungs ,blood vessels, digestive organs and glands.
.It maintains and restores internal homeostasis

70. Sympathetic Nervous System
• Sympathetic stimuli are mediated by nor-epinephrine and
parasympathetic impulses are mediated by acetylcholine.
• Sympathetic neurons are located in the thoracic and the lumbar
segments of the spinal cord ; their axons,or the preganglionic fibres,
Emerge by way of anterior nerve roots from the 8th cervical or the first
thoracic segment to the 2nd or 3rd lumbar segment.

71. Sympathetic syndromes
• Dilatation pf the pupil of the eye on the same side as a penetrating
wound of the neck(evidence of disturbance of the cervical
sympathetic cord).
• Temporary paralysis of the bowel(Indicated by the absence of
peristaltic waves and the distension of the intestine by gas) after
fracture of any one of the lower dorsal or upper lumbar vertebrae
with haemorrhage into the base of the mesentery.
• Marked variations in pulse rate and rhythm that often follow
compression fractures of the upper six thoracic vertebre.

75. • Coordination of movement. The smoothness ,accuracy, and strength
that characterize the muscular movements of a normal person are
attributable to the influence of the cerebellum and basal ganglia.

76. SENSORY SYSTEM FUNCTION
• Integrating sensory impulse
-The thalamus integrates all sensory impulses except olfaction.
-Plays a role in conscious awareness of pain and the recognition of
variation in temperature and touch.
-The thalamus is responsible for the sense of movement and position
and the ability to recognize the size, shape and quality of objects.

77. • Receiving sensory impulses
-Afferent impulses travel from their points of origin to their
destinations in the cerebral cortex via the ascending pathways directly,
or they may cross at the level of the spinal cord or in the medulla ,
depending on the type of sensation that is registered.
-Sensory information may be integrated at the level of the spinal cord
or may be relayed to the brain.

78. • Sensory Losses
-Destruction of a sensory nerve results in total loss of sensation in its
area of distribution.
-Transection of the spinal cord yields complete anesthesia below the
level of injury.
-Selective destruction or degeneration of the posterior columns of the
spinal cord is responsible for a loss of position and vibratory sense in
segments distal to the lesion, without loss of touch, pain, or
temperature perception.