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A&P > Nervous system > Flashcards

Nervous system Flashcards

1
Q

Describe the route a sensory nerve impulse takes from the toe to the brain.

A

Action potential being generated by a specialised sensor
The impulse will travel in an ascending pathway or tract
Different sensory pathways carry different impulses eg pain in the spinal thalamic tract, deep touch in the dorsal column, light touch in the spinal thalamic tract
Axons where they terminate in the medulla - thalamus linking into the limbic system

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2
Q

Compare the central nervous system and the peripheral nervous system.

A

The PNS is made up on neurons that reach every part of the body and consist of:
Cranial nerves which arise from the brain and carry impulses to and from the brain
Spinal nerves - they emerge from the spinal cord to carry impulses to & from the rest of the body
Contain 2 kind of neurons (sensory - afferent) and motor (efferent). The PNS contains somatic voluntary nerves and autonomic - involuntary nerves - these then break down further into sympathetic and parasympathetic states.

The CNS is made up of the brain and the spinal chord. It analyses and stores information, makes decisions and issues orders. It’s where memories are made and stored, emotions generation and thoughts conceived.

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3
Q

Explain the divisions of the nervous system

A

CNS —- PNS
PNS into SOMATIC (VOLUNTARY) and AUTONOMIC (INVOLUNTARY)
Autonomic into SYMPATHETIC and PARASYMPATHETIC

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4
Q

What are the major effects of an activated sympathetic nervous system?

A
  • Pupils dilate
  • Peristalsis is reduced in the stomach, small intestine and large intestine. Sphincters are closed.
  • The liver converts glycogen to glucose at an increased rate
  • The smooth wall of the bladder relaxes
  • Bronchodilation of the trachea and bronchi
  • Vasodilation of the coronary arteries
  • Heart race and force of contractions increase
  • Secretion in the salivary glands is inhibited
  • Vasoconstriction of the blood vessels in the head
  • Adrenaline and noradrenaline is released into the blood from the adrenal medulla
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5
Q

What are the major effects of an activated parasympathetic nervous system?

A
  • Pupils constrict
  • Heart rate and force of contractions decreases
  • Secretion increases in the salivary glands
  • Vasoconstriction in the coronary arteries
  • Bronchoconstriction in the trachea and bronchi
  • Secretion of gastric juice inceases in the stomach
  • Smooth muscle wall of bladder contracts
  • Secretions of peristalsis increases in the small and large intestines, the sphincter is relaxed
  • Blood vessels dilate and secretion of bile increases in the liver
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6
Q

Where on the neuron does the electro-chemical signal occur?

A

It starts in the dendrites on the cell body when stimulated, and passes along the plasma membrane of the axon via an electrical impulse. The chemical signal then occurs at the terminal boutons when it creates a synapse with another neuron.

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7
Q

Explain what the sciatic nerve is?

A

It originates in the lower lumbar & sacral spine segments (L4 - S3)
It innervates most of the muscles of the posterior leg into the foot and branches into other nerves
Its the longest and widest nerve in the whole body

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8
Q

Describe the structure of a nerve

A

A nerve contains:
Neurons wrapped in a protective sheath called ENDONEURIUM bundled together. The outside layer of the bundle is called the PERINEURIUM. This bundle is called a FASCICLE. There are several fasicles within a nerve.
This is then all cased inside a EPINEURIUM.
A nerve also has a strong supply from blood vessels.

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9
Q

What is neuroglia?

A

It is the glue or supporting cells of nervous tissue. They insulate, nurture, protect neurons and maintain homeostasis of the fluid surrounding the neurons. There are 6 types in total (2 IN THE PNS, 4 IN THE CNS).
They do not generate or propagate action potentials.

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10
Q

How many pairs of nerves arise from the cervical spine?

A

8 Pairs
From C1 - C8

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11
Q

What are the 6 types of neuroglia?

A

CNS (4) = Astrocytes, oligodendrocytes, microglia, ependymal cells
PNS (2) = Schwann cells, satellite cells

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12
Q

What is ganglia called when in the CNS?

A

Nuclei (masses of cell bodies)

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13
Q

Where do the parasympathetic nerves arise from?

A

The base of the brain and the sacrum.

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14
Q

How fast is the speed of transmission on a non-mylinated axon?

A

2m per second

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15
Q

How fast is the speed of transmission on a myleinated axon?

A

120m per second using the nodes of ranvier to jump.

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16
Q

What does it mean when a neuron is electrically polarised?

A

positive charged sodium ions on the outside of the membrane, negatively charged potassium ions on the inside of the membrane

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17
Q

What is grey matter?

A

Unmyelinated structures such as neuroglia, cell bodies, axon terminals

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18
Q

What is ganglia?

A

A collection of nerve cell bodies found in the PNS

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19
Q

How many pairs of nerves arise from the sacral spine?

A

5 pairs
S1 - S5

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20
Q

How many pairs of nerves arise from the lumbar spine?

A

5 Pairs
L1 - L5

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21
Q

What is white matter?

A

Myelinated neurons. Myelin is white in colour.

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22
Q

What are nerves or bundles of axons called in the CNS?

A

Tracts or pathways.

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23
Q

How many pairs of nerves arise from the thoracic nerves?

A

12 Pairs.
T1 - T12

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24
Q

How are soidum ions removed out of the inside of the plasma membrane of a neuron?

A

Through sodium ion pumps that quicklu pump out the extra ions, reversing the polarity back to normal. This resets that section of the neuron, moving the impulse forward.

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25
Q

Where do the sympathetic nerves arise from?

A

From the thoracic and lumbar vertebrae

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26
Q

What are plexuses?

A

Webs of nerves that sit around the body.

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27
Q

Describe the somatic nervous system.

A

Soma means BODY.
The SNS allows us to control our skeletal muscles.
Sensory neurons carry impulses from sense receptors to the CNS.
Motor neurons carry impulses from the CNS to the skeletal muscles - this is not always voluntary (reflex arc).

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28
Q

What is depolarisation of the neuron?

A

It’s where the stimulus causes ion channels to open in the plasma membrane, sodium ions flood in causing the inside segment to become positive and the outside negative.
Depolarisation causes the membrane potential to be reversed and this initiates action potential.

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29
Q

What is the function of the nervous system?

A

To link us to the environment through millions of neurons that are sending impulses to eachother, and to control the body, co-ordinate all other body systems and to maintain homeostasis.

30
Q

What are sensory (afferent) neurons?

A

They carry information to the brain and the spinal cord via the cranial and spinal nerves.

31
Q

What are sensory receptors?

A

They detect internal or external stimuli.

32
Q

What is the integrative function of the NS?

A

Perception = The conscious awareness of a sensory stimulus.
Interneurons are used in integration: more of the bodies neurons are interneurons, connecting to nearby neurons.

33
Q

What are motor (efferent) neurons?

A

Information is carried from the brain to the spinal cord and then to muscles of glands resulting in muscle contraction or gland secretion.

34
Q

What is the difference between myelinated and unmyelinated axons?

A

Myelinated axons = surrounded by myelin sheath, a fatty substance which insilates the axon and speeds up nerve impulse transmission. It is formed by schwann cells in the PNS and oligodendrocytes in. the CNS.

Unmyelinated axons = Lack this insulation which results in a slower transmission of nerve impulses.

35
Q

What is demyelination and when does it occur?

A

It’s where the myelin sheath is damaged or destroyed and it disrupts the normal transmission of nerve impulses leading to neurological conditions. This can occur due to autoimmune conditions such as MS, viral infections, metabolic disorders, toxins or trauma.

36
Q

What is the membrane potential?

A

It’s the difference in electric charge across a cell membrane. More positively charged ions outside the cell and more negatively charged ions inside the cell. This difference allows cells to generate electrical signals and perform the transmission of nerve impulses, and maintaining cellular homeostasis.

37
Q

Resting membrane potential

A

It is where the membrane potential of a cell is at rest - therefor not sending signals.

38
Q

Electrochemical gradient

A

This is the combined influence of both the electrical gradient and the concentration gradient across a cell membrane. It determines the strength and direction of ion movement across the membrane.

39
Q

Graded potentials

A

They are local changes in membrane potential that occur in response to stimulation, such as neurotransmitter binding or sensory input.

40
Q

What is the refractor period?

A

It is a brief period immediately following an action potential during which the cell is less responsive to further stimulation. It consists of 2 phases:
The absolute refractor period - no additional action potential can be generated , isn’t capable.
The relative refractory period - where a stronger than usual stimulus is required to generate a new action potential. Ion channel shape alters at the molecular level. K+ channels are open.

41
Q

What is propagation?

A

It’s where an impulse travels from a trigger zone to the axon terminal. The larger the diameter of the axon, the faster the propagated impulse due to the larger surface area.

42
Q

What are the advantages of an electrical impulse?

A
  • Rapid transmission
  • Precise signaling
  • Long distance communication
43
Q

What are the 7 stages of a chemical synapse transmitting a signal?

A
  1. The presynaptic neuron generates an action potential which travels down the axon to the synaptic terminal
  2. Once reached the synaptic terminal, the action potential triggers the opening of voltage-gated calcium channels. Calcium ions influx into the terminal, leading to the fusion of synaptic vesicles containing neurotransmitter molecules into the presynaptic membrane. Neurotransmitters are then released into the synaptic cleft through exocytosis.
  3. Neurotransmitters diffuse across the synapetic cleft and bind to specific receptor molecules on the postsynaptic membrane. These receptors are ligand-gated ion channels.
  4. The binding of the neurotransmitters to receptors causes a conformational change in the receptor protein, leading to opening of ion channels in the postsynaptic membrane.
  5. Postsynaptic potentials can either be depolarizing or hyperpolarizing depending on the neurotransmitter involved. EPSP’s bring the postsynaptic neuron closer to its threshold for firing an action potential, while IPSP’s move the membrane potential away from the threshold.
  6. EPSP’s and IPSP’s generated are integrated at the axon hillock.
  7. Neurotransmitter effects are terminated through enzymatic degradation, reuptake into the presynaptic terminal or diffusion away from the synapse.
44
Q

What is a neurotransmitter?

A

A chemical substance that functions as a signaling molecule in the nervous system. It is released by a presynaptic neuron in response to an action potential and acts on a postsynaptic neuron, muscle cell or gland cell to transmit a signal.

45
Q

Name three neurotransmitters

A

Acetylcholine (ACh)
Dopamine (DA)
Serotonin

46
Q

What is grey matter subdivided into?

A

Horns - The anterior (ventral) horns and posterior (dorsal) gray horns and the lateral gray horns.

47
Q

What do the anterior (ventral) horns contain?

A

Somatic motor nuclei, which provide nerve impulses for contraction of skeletal muscles.

48
Q

What do the posterior (dorsal) gray horns contain

A

Somatic and autonomic sensory nuceli

49
Q

Where are the lateral gray horns found and what do they do?

A

They are only found in the thoracic, upper lumbar and sacral segments of the spinal cord. They contain autonomic motor nuclei that regulate the activity of smooth muscle, cardiac muscle and glands.

50
Q

What is white matter divided into?

A

Three areas called columns.
Anterior (ventral) white columns, posterior (dorsal) white columns and lateral white columns.

51
Q

What do sensory (ascending) tracts consist of?

A

Axons that conduct nerve impulses towards the brain.

52
Q

What do motor (descending) tracts do?

A

Carry nerve impulses from the brain

53
Q

Describe the nerve root

A

The point of origin of a spinal nerve from the spinal cord. Consists of both motor and sensory fibers.

54
Q

Describe the nerve branch

A

It is a smaller division or subdivision of a nerve that arises from a main nerve trunk or a larger nerve. They can occur at various points along the length of a nerve and supply specific regions or structures with motor, sensory or autonomic innervation.

55
Q

Describe plexuses

A

They are networks or meshworks of intersecting nerves. They are associated with a specific region of the body and serves to distribute motor, sensory, and autonomic innervation to that region.

56
Q

What is the main nerve in the cervical plexus?

A

Phrenic nerve

57
Q

What are the main nerves in the brachial plexus?

A

Musculocutaneous nerve
Axillary nerve
Median nerve
Radial nerve
Ulnar nerve

58
Q

What nerves sit between the ribs?

A

Intercostal nerves

59
Q

What are the main nerves from the lumbar plexus?

A

Ilioinguinal nerve
Femoral nerve
Obturator nerve

60
Q

What are the main nerves from the sacral plexus?

A

Superior gluteal nerve
Interior gluteal nerve
Pudendal nerve

61
Q

What is a dermatome?

A

The area of skin that provides sensory input to the CNS via one pair of nerves. Can be used diagnostically if a patient has numbness in a specific area.

62
Q

What are the five functional components of a reflex arc?

A
  1. The receptor detects a stimulus and generates sensory input in response to it.
  2. The sensory neuron carries the sensory input from the receptor to the CNS.
  3. The integration centre in the CNS processes the sensory input received from the sensory neuron and generates a motor response. This may involve synapses between sensory neurons and interneurons.
  4. The motor neuron carries the motor output from the integration center to the effector organ or tissue.
  5. The effector is the muscle, gland or organ that carries out the response generated by the integration center.
63
Q

What anatomical or physiological structures protect the brain?

A

The skull - protective enclosure for the brain, sheilding it from physical trauma and injury

Meninges - These are 3 layers of protective membranes around the brain. They include the DURA MATER (outermost layer), ARACHNOID MATER (middle layer) and PIA MATER (intermost layer). They provide support, cushioning and stability to the brain and spinal cord.

Cerebrospinal fluid - Clear, colourless fluid that surrounds the brain and spinal cord within the subarachnoid space. It has shock absorption, buoyancy and the removal of metabolic waste products from the CNS.

Blood brain barrier - Highly selective semipermeable membrane barrier separating blood from extracellular fluid.

Cranial nerves - These are a set of 12 pairs of nerves that emerge directly from the brain and primarily innervate structures of the head and neck. Important for sensory perception and motor control.

64
Q

What three things make up the brain stem?

A

Medulla oblongata - regulates autonomic functions eg breathing, heart rate, blood pressure.

Pons - Helps regulate breathing, contains nuclei involved in sleep, swallowing, facial movements. Acts as a bridge between different parts of the brain.

Midbrain - A relay centre for auditory and visual reflexes, contains nuclei involved in motor control, arousal and temp regulation

65
Q

Whats the function of the cerebellum?

A

It coordinates voluntary movements, balance and posture. Helps fine-tune motor activities.

66
Q

What three parts make up the Diencephalon?

A

Epithalamus - contains pineal gland which produces melatonin and regulates circadian rhythm

Thalamus - Relay station for sensory information. Plays role in regulating consciousness, sleep and alertness.

Hypothalamus - regulates homeostasis by controlling autonomic functions eg. body temp, thirst, hunger. Also regulates emotional responses.

67
Q

Describe the cerebrums function

A

Responsible for higher cognitive functions including perception, thought, memory and voluntary movement. It is the largest part of the brain.

68
Q

What is the structure and function of the limbic system?

A

It is a network of brain structures which regulates emotions, motivation and memory. It integrates sensory information with emotional states, influences behaviour and conscious experience.

Key areas include:
- Hippocampus for memory consolidation
- Amygdala for emotion processing and memory
- Hypothalamus for physiological regulation
- Cingulate cortex for emotional and cognitive control

69
Q

What are the 12 pairs of cranial nerves?

A
  1. Olfactory
  2. Optic
  3. Oculomotor
  4. Trochlear
  5. Trigeminal
  6. Abducens
  7. Facial
  8. Vestibulocochlear
  9. Glassopharyngeal
  10. Vagus
  11. Accessory
  12. Hypoglossal
70
Q

What fills the central canal of the spinal cord?

A

Cerebrospinal fluid

71
Q

What happens to the propagated impulse when the diameter of the axon increases?

A

Increases in speed

A&P (13 decks)

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