EXER 5: NERVOUS SYSTEM

Neuron or Nerve cell

- functional unit of the nervous system

Neuron or Nerve cell

conduction of transmission of impulses from the peripheral organs to the CNS or vice versa.

1. Nerve cell body/Soma/Cyton

2. Processes

Parts of a Neuron (2)

Nerve cell body/Soma/Cyton

synonymous with the cytoplasm, nucleus and nucleoli of cell

Neuroplasm

specific term for the cytoplasm of neurons 

• organelles present are mitochondria, fibrils, golgi apparatus 

• inclusion present are Nissi bodies or tigroid bodies, fats, pigments

Processes

cytoplasmic extension responsible for the conduction of impulses

Synapse

• point of contact between neurons which are functionally related important for the conduction of impulses

• Axo-axonal

• Axon-dendrite

• Dendrite-dendrite

Synapse (3)

1. Unipolar - 1 process (axon)

2. Bipolar - 2 processes (axon+dendrite)

3. Multipolar - 3 or more processes (axon +2 or more dendrites)

4. Pseudounipolar - 2 processes (axon+dendrite fused, appear only 1 process

Classification of neuron (4)

Central NS

Brain and spinal cord

Brain

enclosed by the cranium of skull

Spinal cord

enclosed in vertebral canal

1. caudal continuation of medulla oblongata

2. gives rise to paired spinal nerves

1. Dorsal roots/branch of spinal nerves

2. Ventral roots/branch of spinal nerves

Spinal cord (2)

Dorsal roots/branch of spinal nerves

• receives sensory (afferent) fibers

• carry motor impulses from spinal cord to striated muscles

• supply nerve impulses to structures dorsal to transverse processes of vertebrae

Ventral roots/branch of spinal nerves

• gives off motor (efferent) fibers

• carry motor impulses from spinal cord to striated muscles

• supply nerve impulses to structures ventral to transverse processes of vertebrae, forelimb and hind limb

Peripheral NS

Composed of spinal nerves, cranial nerves and autonomic nervous system

1. Prosencephalon

2. Mesencephalon

3. Rhombencephalon

Division of brain (3)

Prosencephalon

forebrain

1. Telencephalon

2. Diencephalon

Prosencephalon (2)

Telencephalon

encloses the cavities of the lateral ventricles, interventricular foramina of Monro and rostral part of 3rd ventricle

Cerebrum

• divided into left and right cerebral hemispheres by a longitudinal fissure

gyri

• divided into left and right cerebral hemispheres by a longitudinal fissure

sulci

• furrows separating the gyri of cerebrum

Telencephalon

• voluntary muscle control o interpretations of sensation o reasoning

• higher learning

• Rhinecephalon/Olfactory brain

• = part of cerebrum composed of olfactory bulb and peduncle

• Function: sense of olfaction or smell

Diencephalon

associated with 3rd ventricle

Thalamus

• composed of nerve fibers or axons

  • Function: connects the cerebrum with the brain stem and spinal cord

Epithalamus

• Most specially contains the pineal gland - endocrine gland important for seasonal breeders and circadian rhythm

Hypothalamus

• Functions:

  • regulation of secretion of endocrine glands o thermoregulation

  • controls feeding, drinking and satiety

1. Thalamus

2. Epithalamus

3. Hypothalamus

Diencephalon (3)

Mesencephalon

midbrain part of brain that does not divide during development

Mesencephalon

• Located between the diencephalon rostrally and rhombencephalon caudally

Rhombencephalon

hindbrain, associated with 4th ventricle

1. Metencephalon

2. Myencephalon

Rhombencephalon (2)

Metencephalon

rostral part of rhombencephalon

1. Cerebellum

2. Pons

Metencephalon (2)

Cerebellum

• surface of cerebellum consists of laminae called folia

Pons

• located ventral to the cerebellum

Myencephalon

caudal part of rhombencephalon, Brain stem

Myencephalon

• Medulla oblongata

• Cranial continuation of spinal cord

• Brain stem - site of nuclei for cranial nerves 3-12

Ventricles

All derived from the embryonic neural canal, contains the fluid called cerebrospinal fluid (CSF) which is formed by the choroid plexus (network of blood vessels particularly capillaries) of the ventricles and in the subarachnoid space surrounding the brain and spinal cord

Cerebrospinal fluid (CSF)

- acts as a protective cushion for the brain and spinal cord

1. Lateral ventricles -

2. Interventricular foramina of Monro -

3. 3rd ventricle -

4. Aqueduct of Sylvius -

5. 4th ventricle -

6. Foramen of Luschka -

Ventricles (6)

1. Lateral ventricles -

located within the left and right cerebral hemispheres

1. Interventricular foramina of Monro -

connects lateral ventricles with 3rd ventricle

1. 3rd ventricle

- most parts are surrounded by diencephalon, a part projects into the pituitary gland

1. Aqueduct of Sylvius

- connects 3rd and 4th ventricles

1. 4th ventricle

1. - located ventral to cerebellum, dorsal to pons and medulla

1. Foramen of Luschka

- communication between 4th ventricles with subarachnoid space

Meninges

Covering of the brain and spinal cord (outermost to innermost)

Durameter

1. outermost fibrous covering of the CNS which blends intimately with the inner periosteum of the cranial bones of skull or vertebrae

Durameter

• protects brain

• possess sinuses which are veins that carry blood from brain back to heart

Arachnoid

1. middle layer

Subarachnoid space

1. space which separates arachnoid from pia

Pia meter

1. innermost layer; selective entry and exit of chemicals between brain and blood

Peripheral NS

Composed of spinal nerves, cranial nerves and autonomic nervous system

1. Durameter -

2. Arachnoid -

3. Subarachnoid space -

4. Pia meter -

Meninges (4)

Spinal nerves

emerge through intervertebral foramina

Spinal nerves

1. Cervical nerves = 8 pairs

2. Thoracic nerves = corresponding number of thoracic vertebrae (pair)

3. Lumbar nerves = corresponding number of lumbar vertebrae (pair)

4. Sacral nerves = corresponding number of sacral vertebrae (pair)

5. Caudal nerves = fewer than the caudal vertebrae (pair)

Brachial plexus

network of nerves derived from ventral branches cervical and thoracic nerves supplies the forelimb

Cow, sheep, pig

• Derivation of Brachial Plexus: C6-8 & T1

Horse

• Derivation of Brachial Plexus: C6-8 & T1-2

Lumbersacral plexus

network of nerves derived from ventral branches of lumbar and sacral nerves supplies the hindlimb

Horse, cow, sheep

Derivation of lumbosacral Plexus: Last 3 lumbar & S1-2

Pig

Derivation of lumbosacral Plexus: Last 3 lumbar & S1

Autonomic NS

Part of PNS which innervates smooth muscles, cardiac muscles and visceral organs

1. Sympathetic NS

2. Parasympathetic NS

Divisions of Autonomic NS

Sympathetic NS

• thoracolumbar part, sympathetic innervation of organs and structures 

• short preganglionic fibers, long postganglionic fibers, synapse in ganglions 

  • sympathetic trunk, cervical ganglions, celiac ganglion, cranial mesenteric, caudal mesenteric ganglion, splanchnic nerves

Parasympathetic NS

• craniosacral part, parasympathetic innervation of organs and structures 

• long preganglionic fibers (ganglions near organs), short postganglionic fibers

• involves cranial nerves 3,7, 9, 10