nervous system for undergraduate

1. Nervous System
• The human brain is the most complex tissue in the
body.
• It mediates behavior ranging from simple movements
and sensory perception to learning, memory, and
consciousness.
• Many of the brain's functions are poorly understood
• the most prominent function of the human brain-
capacity to think
1

2. Classification of NS
NS
CNS
Brain Spinal cord
PNS
Sensory
Special(elicited from
specific parts)
Vision, olfaction, test ,hearing
& sense of balance
General(elici
ted from d/t
parts)
Somatic sensation
Elicited from skin,
subcutaneous tissue,
tendon and SM
(locomotors system)
T0,touch, pain,
proprioception
Visceral
sensation
From
visceral
organ,
Distention,
dull pain
Motor
somatic
(Voluntary) from
Skeletal
Autonomic (involuntary)
from smooth cardiac and
glands
SNS PSNS
2

3. Subdivisions of the Nervous System
SUBDIVISION COMPONENTS SPECIAL FEATURES
Central
Brain (including CN II and retina) and
spinal cord
Oligodendrocytes provide
myelin
Axons cannot regenerate
Peripheral
Peripheral ganglia (including cell
bodies); sensory receptors; peripheral
portions of spinal and cranial nerves
(except CN II), both afferent and
efferent
Schwann cells provide
myelin
Axons can regenerate
3

4. Cont …
1. The central nervous system (CNS)-
 consists of the brain and spinal cord .
 It is covered by three “membranes”—the meninges.
 The outer membrane is the dura mater;
 the middle is the arachnoid and
 the inner membrane is called the pia mater.
 Within the CNS, some neurons that share similar
functions are grouped into aggregations called nuclei.
 The CNS can also be divided into;
 gray matter- neuron cell bodies and
 white matter- myelin
4

5. Cont…
2. The peripheral nervous system (PNS) consists of those parts
of the nervous system that lie outside the dura mater.
• These elements include
– sensory receptors for various kinds of stimuli
– the peripheral portions of spinal and cranial nerves and
– all the peripheral portions of the autonomic nervous
system.
• The sensory nerves that carry messages from the periphery to
the CNS are termed afferent nerves
• the peripheral motor nerves that carry messages from the
CNS to peripheral tissues are called efferent nerves
• Peripheral ganglia are groups of nerve cells outside the CNS.
5

6. Cont…
3. The autonomic nervous system (ANS) is that
portion of the nervous system that regulates and
controls visceral functions.
• Including heart rate, blood pressure, digestion,
temperature regulation, and reproductive
function.
• Although the ANS is a functionally distinct
system, it is anatomically composed of
parts of the CNS and PNS.
6

7. Neuron doctrine
• Asserted that the nervous system is composed of many individual signaling
units—the neurons.
• In 1838, Schleiden and Schwann proposed that the nucleated cell is the
fundamental unit of structure and function in both plants and animals.
• 1885, when Camillo Golgi introduced his silver impregnation method, “the black
reaction,” there was no clear indication that the brain is composed of
individual cells.
• The histologist Santiago Ramón y Cajal worked relentlessly with the silver-staining
method and eventually concluded that not only is nervous tissue composed of
individual cells.
• Also he stated that the tapering branches near the cell body are the receptive end
of the cell, and the long-axis cylinder conveys signals away from the cell.
Santiago Ramón y Cajal
For more information about Santiago Ramón y Cajal and the work that led to his
Nobel Prize, visit http://www.nobel.se/medicine/laureates/1906/index.html
7

8. • Nerve cells have four specialized regions:
– Cell body-housekeeping functions
– Dendrites-receiving information
– Axon-message-sending and
– Presynaptic terminals
8

9. CSF communicates freely with the
BECF
• Freely communicate across two borders;
1. the pia mater and
2. ependymal cells.
Because the form gap junction
9

10. BBB
• The small brain areas that lack a BBB are called the
circumventricular organs.
 because they surround the ventricular system;
• these areas include the area postrema, posterior
pituitary, median eminence, organum vasculosum
laminae terminalis, subfornical organ, subcommissural
organ, and pineal gland and
• Choroid plexus
• this arrangement is believed to be part of a
neuroendocrine control system, leakiness is important
in the action of cytokines
10

11. Cont….
11

12. Cont…
• Substances that cross BBB are;
 gases such as CO2 and O2
 drugs such as ethanol, caffeine, nicotine, heroin, and
methadone and
 H2O.
• Substances not cross BBB are;
 However, ions such as K+ or
Mg2+ and protein-bound metabolites such as bilirubin
12

13. Intra cranial pressure
• Caused mostly by trauma
• By glutamate neurotransmitter
 B/S as glutamate binds with inotropic
receptor it increases Na+ flow
• Management of ICP
Hyperventilation cause respiratory alkalosis
and vasoconstriction
Mannitol
13

14. Glial cells
• In CNS oligodendrocye, microglia and
astrocyte
• In PNS Schwann cell and satellite cell
• Severed axons in the CNS do not show
functional regrowth, in part because of the
growth-retarding nature of myelin-associated
glycoprotein.
14

15. Synaptic Transmission
• Named by Charles Sherrington
• All skeletal neuromuscular junctions use
acetylcholine (ACh).
• In contrast, neuronal synapses use many
transmitters.
• The most common are;
glutamate and aspartate excite whereas
gamma-aminobutyric acid (GABA) and glycine
inhibit
15

16. ANS
Output from the central nervous system (CNS)
1. somatic motor
- To skeletal muscles
2. Autonomic motor neuron
- self-governing,” functioning independently of the
will
- To cardiac ,smooth, secretary epithelial and
glands
16

17. ANS…
• The ANS has three divisions:
1. Sympathetic
- occurs under conditions such as stress, anxiety, physical activity,
fear, or excitement,
2. parasympathetic and
- increases during sedentary activity, eating, or other “vegetative”
behavior.
3. enteric.
- Neutrons that surround the gastrointestinal (GI) tract.
• The sympathetic and parasympathetic divisions are most common
one
17

18. ANS…
• The cell bodies of the first neurons lie within
the CNS.
• These preganglionic neurons are found in the
brainstem and spinal cord and send axons out
of the CNS to make synapses with
postganglionic neurons
• Axons from these postganglionic
neurons then project to their targets.
18

19. 19

20. 20

21. 824
21