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Introduction to the Nervous System Flashcards

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1
Q

What Do Nerves Do?

A

Sensory Functions: Enable us to perceive internal and external environments.

Special Senses: Vision, hearing, taste, smell, and balance

Motor Functions: Facilitate appropriate responses to stimuli.

  • Voluntary: Skeletal muscle movement (locomotion)
  • Involuntary: Smooth muscle, gland, and cardiac muscle actions
    Reflex Functions: Automatic, rapid responses to stimuli.
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2
Q

Anatomical Subdivisions

A

Central Nervous System
Peripheral Nervous System

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3
Q

Describe the CNS

A

Brain
Spinal Cord
Central controller

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4
Q

Describe the PNS

A

All other nerve tissue not within the CNS
Spinal nerves
-connect with spinal cord
Cranial nerves
-connect with brain
Autonomic nerves
-organs, smooth muscle, glands
-visceral afferents
-sympathetic nerves
-parasympathetic nerves
Wiring

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5
Q

Describe The Neuron

A

Basic unit of nervous system
Collection of nerve cell bodies:
in CNS = Nucleus
in PNS = Ganglion

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6
Q

Describe Nerves

A

Bundles of Axons (nerve fibres): Wrapped in connective tissue, traveling to/from same regions or structures.
Can branch off as smaller bundles
Named Nerves: Larger nerves serving the body wall, cavities, and organs

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7
Q

What is in a Nerve?

A

A single nerve fiber (axon) only conducts action potentials for ONE of six modalities:
1. Somatic sensory function
2. Somatic motor function
3. Special sensory function
4. Visceral afferent function
5. Sympathetic function
6. Parasympathetic function

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8
Q

Motor Vs Sensory

A

Motor (efferent):
Action potential towards body wall, body cavity or organ
Sensory (afferent):
Action potential towards brain

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9
Q

Describe The Brain

A

outermost layer of the cerebral hemispheres cortex
consists of gyri and sulci

4 lobes of each cerebral hemisphere
named according to cranial bone they lie deep to

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10
Q

What is the Cranial Nerves

A

12 pairs - need to know name, number (Roman numerals), modality and function(s), where they connect to CNS, route through and exit from cranium

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11
Q

CN I

A

-olfactory nerve
-sensory (special)

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12
Q

CN II

A

optic nerve
sensory (special)

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13
Q

CN III

A

oculomotor nerve
motor (somatic & parasym.)

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14
Q

CN IV

A

trochlear nerve
motor

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15
Q

CN V

A

trigeminal nerve
both

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16
Q

CN VI

A

abducent nerve
motor

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17
Q

CN VII

A

facial nerve
both (spec.sensory, somatic motor & parasym.)

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18
Q

CN VIII

A

vestibulocochlear nerve
sensory (special)

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19
Q

CN IX

A

glossopharyngeal nerve
both (spec.sensory, somatic motor & parasym.)

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20
Q

CN X

A

vagus nerve
both (somatic sensory, somatic motor & parasym.)

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21
Q

CN XI

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A

spinal accessory nerve
motor

22
Q

CN XII

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A

hypoglossal nerve
motor

23
Q

Where Cranial Fossae Foraminae for CNs to enter/exit cranial cavity:

24
Q

Course of a Cranial Nerve

25
The Spinal Cord
Passes through **foramen magnum** Protected by **vertebral canal** *Has 4 segments:* **cervical thoracic lumbar sacral/coccygeal** Has 2 enlargements **cervical lumbosacral** Connects **bilaterally with spinal nerves** 8 cervical - C1-C8 12 thoracic - T1-T12 5 lumbar - L1-L5 5 sacral - S1-S5 1 coccygeal - Co spinal cord ends at L1/L2 IV disc level conus medullaris Adult vertebral column is longer than the adult spinal cord lumbar and sacral spinal nerve roots have to descend in the vertebral canal to their respective intervertebral foraminae cauda equina (horse’s tail)
26
How are Spinal nerves named?
* according to the vertebrae above it * except in the cervical region, where they are named according to the vertebrae below it * C8 spinal nerve exits between C7 and T1 vertebrae
27
Vertebral Column
33 vertebrae in total 7 cervical 12 thoracic 5 lumbar 5 sacral fused to form 1 sacrum 4 coccygeal fused to form 1 coccyx
28
Rules of spinal nerve anatomy:
* spinal nerves supply the soma (body wall) * located only within the intervertebral foramina * from the intervertebral foramina they connect with * structures of the soma via rami * the spinal cord via roots and rootlets
29
Anatomy of Spinal Nerves
30
Spinal Nerves and Body Segments
each pair of spinal nerves supplies one ‘strip’ of the soma **posterior rami** -supply small posterior strip **anterior rami** -supply the remainder of the posterior part, the lateral and the anterior parts of the strips -supply all of the limbs
31
What is a Dermatomes
area (strip) of skin supplied by both the anterior and posterior rami of a spinal nerve T4 dermatome – nipple T10 dermatome – umbilicus
32
List Nerve Plexuses
**Cervical plexus** C1-C4 anterior rami Posterior scalp, neck wall and diaphragm **Brachial plexus** C5-T1 anterior rami Upper limb **Lumbar plexus** L1-L4 anterior rami Lower limb **Sacral plexus** L5-S4 anterior rami Lower limb, gluteal region and perineum
33
Functional Subdivisions - Somatic nervous system
***Soma includes:*** -head and neck walls -chest walls -back -the diaphragm -abdominal wall -pelvic wall -limbs ***Structures:*** -skin -fascia -skeletal muscle -skeleton -internal lining of body cavities
34
Somatic Sensation- Sensations felt by body wall
**sensed by mechanoreceptors:** -coarse touch -fine touch -vibration -proprioception **sensed by thermoreceptors:** -temperature **sensed by nociceptors:** -pain
35
Describe Somatic Sensation
* Somatic sensory mechanoreceptors in the L2 dermatome are stimulated * Action potentials (APs) travel via axons in the L2 anterior ramus * These axons pass through the lumbar plexus to the L2 spinal nerve * APs continue through the dorsal (posterior) root ganglion, dorsal roots, and rootlets * APs reach the posterior horn of the L2 spinal cord segment * APs cross the midline and ascend towards the brain
36
Describe Motor Innervation
Somatic motor axons cross in the brainstem and descend to the anterior horn. APs travel through anterior rootlets, roots, and spinal nerves. APs continue via lumbar plexus nerves to synapse on lower limb skeletal muscles. Skeletal muscles contract, moving the lower limb.
37
Spinal Reflexes
-reflex is extremely rapid -misses out pathway to brain -involuntary response
38
Functional Subdivisions - Autonomic nervous system
***Includes*** Viscera e.g. heart, lungs, intestines, kidneys glands (mucous, sweat, salivary etc.) smooth & cardiac muscle external lining of organs ***Locations*** internal organs in body cavities chest cavity, pelvic cavity, abdominal cavity ***body wall organs*** sweat glands, arrector smooth muscles, arterioles
39
Describe the Autonomic Nervous System
Auto = self , nomos = law Internal environment: -Sensory neurones -Sensations from organs to CNS -Motor Neurones
40
Role of Sensory neurones in ANS
sense the internal environment (organs) organs sensory nerves are called ‘visceral afferent’
41
Role of Sensations from organs to CNS in ANS
-Touch -Temperature -Pain -Ischaemic -Colicky Described as: – dull, achy, nauseating - poorly localised
42
Role of Motor Neurones in ANS
-**respond** to changes in internal environment **dual motor control** -Many internal organs have both a **sympathetic & parasympathetic** nerve supply -Both motor controls -‘Accelerator’ or ‘brake’
43
3 Things Sympathetic Division of ANS supplies
* all internal organs * body wall organs * arterioles
44
How do the following structures respond during ‘Flight or fight’ | pupils, heart, lungs. GI tract, Liver, Adrenal Glands, Arterioles, Skin
Pupils - dilate Heart - rate increases Lungs - bronchioles dilate GI tract - motility is reduced Liver - glucose released into the blood Adrenal glands - adrenaline/noradrenaline released Arterioles - dilate or constrict- skin feels cold & looks pale Skin - hair stands on end & sweat produced
45
Describe Sympathetic Outflow
Descends the spinal cord and exits with T1-L2 spinal nerves. Travels to sympathetic chains along the vertebral column. Distributes via spinal nerves, anterior/posterior rami, to body wall structures. Follows arteries to supply head, neck, and skin. Travels via splanchnic nerves to reach organs.
46
Which segments of the spinal cord have lateral horns and why?
T1- L2 for cell bodies of the next sympathetic neurones in the chain
47
Parasympathetic Division of ANS
Often supplies **same internal organs** as sympathetic division **Does not supply body wall organs or arterioles** **Rest & Digest** -Returns to homeostasis -Compliments / Opposes the sympathetic system
48
How do the following structures respond during ‘Rest and Digest' | pupils, heart, lungs, GI tract, liver, bladder
Pupils - constrict Heart - rate decreases Lungs - bronchioles constrict GI tract - motility is increased Liver - glucose synthesis Bladder – sphincter relaxes
49
Describe Parasympathetic Outflow
* Parasympathetic axons exit via cranial nerves III, VII, IX, X, and sacral spinal nerves. * Target internal organs, not the body wall. * Cranial ganglia supply the lacrimal and salivary glands. * Vagus nerve innervates neck, chest, and mid-gut organs. * Sacral nerves carry axons to the hindgut, pelvis, and perineum
50
Modalities – Neuron Types

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