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Nervous System

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Nervous System FUNCTIONS: Sensory input. Integration. Homeostasis. Mental activity. Control of skeletal muscles. – PowerPoint PPT presentation

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Title: Nervous System


1
Nervous System
  • FUNCTIONS
  • Sensory input.
  • Integration.
  • Homeostasis.
  • Mental activity.
  • Control of skeletal muscles.

2
The Nervous System
3
Organization of the Nervous System
  • Central nervous system (CNS)
  • Brain and spinal cord
  • Peripheral nervous system (PNS)
  • Neurons outside the CNS
  • Sensory division
  • Afferent fibers transmit impulses from receptors
    to CNS
  • Motor division
  • Efferent fibers transmit impulses from CNS to
    effector organs

4
Relationship between motor and sensory fibers of
the PNS and the CNS
5
Autonomic Nervous System
  • Sympathetic
  • Fight or flight, stress
  • Excitatory effects elicited by norepinephrine
    activating beta receptors
  • Inhibitory effects elicited by activation of
    alpha receptors

6
  • Parasympathetic
  • Rest and digest
  • Digestive system activated, heart rate inhibited,
    blood vessels dilated
  • Vagus nerve primarily responsible for activating
    parasympathetic responses

7
Fig. 8.39
8
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9
Synapse
  • Specialized site of intercellular communication.
  • 3 Components
  • 1. Presynaptic terminal
  • 2. Synaptic cleft
  • 3. Postsynaptic membrane

10
Functional Organization of the Nervous System
11
The Neuron
12
Neuroglia
13
Neuroglia
  • Accessory cells of the nervous system
  • Astrocytes
  • Support tissue in the CNS form blood-brain
    barrier
  • Ependymal
  • Produce and move cerebral spinal fluid
  • Microglia
  • Remove cell debris and bacteria from CNS
  • Oligodendricytes and Schwann cells
  • Provide insulation around axons of CNS and PNS
    neurons

14
Myelinated vs. Unmyelinated Axons
15
Membrane Potentials
  • Nervous system functions by establishing
    concentration gradients and electrical potentials
    across the membranes
  • The resting membrane potential of a neuron is
    negative and is said to be polarized
  • These gradients are maintained by the sodium
    potassium pump

16
Concentration Gradients and Nerve Cell Function
17
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18
Action Potentials
  • Muscle and nerve cells are exciteable
  • When a muscle or nerve cell is stimulated Na
    channels open and Na rushes into the cell
  • This causes a local potential
  • This local potential may not result in action
    potential
  • Doesnt cross the threshold

19
  • If the stimulus is sufficient to cause the local
    potential to cross the threshold an action
    potential results
  • The action potential is the complete
    depolarization of the cell
  • The action potential is an all-or-nothing event
  • If the local potential meets threshold, the cell
    totally depolarizes and the action potential
    results
  • If the potential does not meet threshold, no
    action potential results

20
Fig. 8.9
21
Fig. 8.10
22
Action Potential Propogation
  • Unmyelinated neurons propogate signals more
    slowly than myelinated neurons
  • Myelination acts as an insulator
  • Electrical signal will jump from node of Ranvier
    to node of Ranvier
  • This is called saltatory conduction
  • Requires less energy than direct propogation

23
Propagation of the Action Potential
24
Synapse
  • Electrical --rare
  • Chemical
  • --communication occurs in one direction
  • presynaptic membrane to postsynaptic membrane
  • --action potential is not always propagated.

25
Synapse
  • Synapses may occur
  • neuron to neuron
  • neuron to another type of cell (neuroeffector) --
    neuromuscular junction
  • --neuroglandular junction

26
Fig. 8.13
The Synapse
27
Neurotransmitters
  • --packaged in synaptic vesicles.
  • Nerve endings of the ANS secrete
  • Acetylcholine (ACh)--Cholinergic neuron
  • Parasympathetic effector
  • Norepinephrine (NE)--Adrenergic neuron
  • Sympathetic effector

28
  • Neurotransmitters diffuse across the synaptic
    cleft and bind to receptor on the post-synaptic
    membrane
  • This can cause membrane channels (Na, K, or
    Cl-) to open or close depending on the
    neurotransmitter
  • If stimulatory, Na channels will open
  • If inhibitory, K or Cl- channels will open
  • Cell becomes more negative, hyperpolarized

29
Receptors
  • 2 types of cholinergic receptors
  • Nicotinic
  • Preganglionic sympathetic and parasympathetic
  • Muscarinic
  • parasympathetic
  • 2 types of adrenergic receptors
  • Alpha
  • Generally inhibitory
  • Beta
  • Generally excitatory

30
Autonomic Reflex Arc
  • 1. Receptor
  • 2. Sensory neuron
  • 3. Association neuron
  • 4. Autonomic motor neuron
  • 5. Visceral effector

31
Reflex Arc
32
Knee Jerk Reflex
33
Converging Circuit
34
Central Nervous System
  • Adult
  • Brainstem
  • --medulla oblongata
  • --pons
  • --midbrain
  • Diencephalon
  • --thalamus
  • --hypothalamus
  • --epithalamus
  • Cerebrum
  • Cerebellum

35
Brainstem
  • Medulla oblongata
  • Inferior portion
  • Regulation of heart rate, venoconstriction,
    ventilation, swallowing, , etc..
  • Pons
  • Superior to medulla
  • Bridge between cerebrum and cerebellum
  • Midbrain
  • Audio and visual processing

36
Cerebellum
  • Integrates motor signals from cerebral cortex
    with feedback from PNS
  • Proprioception
  • Learning tasks

37
Dienchephalon
  • Thalamus
  • Sensory input from PNS passes through thalamus
    (relay station)
  • Epithalamus
  • Pineal gland sleep cycle, puberty
  • Hypothalamus
  • Master gland
  • Attached to pituitary by infundibulum
  • Controls much of homeostasis by stimulating or
    inhibiting pituitary

38
Cerebrum
39
Brain Protection
  • cranial bones
  • cranial meninges
  • cerebrospinal fluid
  • neuroglia (astrocytes)

40
The Brain
41
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42
CEREBRUM
  • Largest part of the brain thinking part
  • Markings
  • Gyrus (gyri)-- wrinkle, raised area
  • Fissure(s)-- deep, wide groove(s)
  • Sulcus (sulci)-- shallow groove(s)

43
CEREBRUM
  • Lobes
  • 1) Frontal
  • 2) Parietal
  • 3) Temporal
  • 4) Insular
  • 5) Occipital

44
CEREBRUM
  • Displays lateralization
  • left hemisphere
  • language math/science reason
  • right hemisphere
  • music/art spatial relations
    insight/imagination

45
CEREBRUM
  • sensory areas
  • motor areas
  • association areas

46
Spinal Cord-- Composition
  • white matter (myelin)
  • dorsal column
  • ventral column
  • lateral column
  • gray matter (non-myelin)
  • posterior horn
  • ventral horn
  • lateral horn

47
Spinal Cord-- White Matter
  • myelinated axons that travel along the spinal
    cord.
  • Ascending-- up cord to higher levels
  • Descending-- down cord from brain
  • Across the cord

48
Spinal Cord
  • Dorsal roots (sensory)
  • Ventral roots (motor)
  • combine to form spinal nerve.
  • Dorsal Root Ganglion

49
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50
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51
Peripheral Nervous System
  • Cranial Nerves
  • 12 pr.-- I to XII (anterior to posterior)
  • 3 functions
  • 1) sensory
  • 2) somatic-- control of skeletal muscle
  • 3) parasympathetic--regulation of glands,
    smooth muscle, and cardiac muscle.

52
Peripheral Nervous System
  • Spinal Nerves
  • 31 pr. 8 cervical
  • 12 thoracic
  • 5 lumbar
  • 5 sacral
  • 1 coccygeal

53
SPINAL NERVES
  • rootlets ? roots ? spinal nerve ? ramus
  • Dorsal rami
  • Ventral rami--
  • Distributed 2 Ways
  • Intercostal nerves (T1-T12)
  • Plexuses (5) cervical plexus (C1-C5)
  • brachial plexus (C5-T1)
  • lumbar plexus (L1-L4)
  • sacral plexus (L4-S4)
  • coccygeal plexus (S4, S5, Cx)
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