Topic 2 - The Nervous System Flashcards
(90 cards)
1
Q
What are neurons?
A
Basic structural and functional unit of the nervous system.
2
Q
What are nerve fibres?
A
Any long extension of a nerve cell.
3
Q
What are nerves?
A
They are bundles of nerve fibres held together by connective tissue.
4
Q
What are neurons made out of?
A
- Cell body
- Dendrites
- Axon
- Myelin sheath
- Axon terminals
5
Q
What is the cell body?
A
Contains nucleus and controls cell activities.
6
Q
What are dendrites?
A
Short extensions of the cytoplasm that receive messages from other neurons and carries information away from the cell body.
7
Q
What is the axon?
A
A single long extension of the cell body that transmits impulses away from the cell body.
8
Q
What is the myelin sheath?
A
Layer of fatty tissue thst covers most axons. Its main functions are:
- Act as an insulator
- Protects axon from damage
- Increases speed of nerve impulses
9
Q
What are axon terminals?
A
Release neurotransmitters to send signals to the next neuron.
10
Q
What are neurilemmas?
A
The outermost layer that surrounds the myelin sheath that aids in the repair of damaged nerve fibres.
11
Q
What are the nodes of ranvier?
A
Gaps in the myelin sheath.
12
Q
What are synapses?
A
Small gaps between 2 adjacent neurons.
13
Q
What is the neuromuscular junction?
A
The gap that exists where an axon meets a skeletal muscle cell.
14
Q
What is a ganglia?
A
Cell bodies located in the peripheral nervous system.
15
Q
What are oligodendrocytes?
A
Cells that form the myelin sheaths within the CNS.
16
Q
What are schwann cells?
A
The outer part of schwann cells form the myelin sheaths in the PNS.
17
Q
What are the 3 functional types of neurons?
A
1) Sensory neurons
2) Motor neurons
3) Interneurons
18
Q
What are sensory neurons?
A
Carry signals from receptors to the CNS.
19
Q
What are motor neurons?
A
Carry signals from the CNS to effectors (muscles/glands).
20
Q
What are interneurons?
A
Connect sensory and motor neurons within the CNS.
21
Q
What is the structure of a unipolar neuron and a example?
A
One axon, no dendrites. This is not found in humans.
22
Q
What are the structural types of neurons?
A
1) Unipolar
2) Multipolar
3) Bipolar
4) Pseudo-unipolar
23
Q
What is the structure of a multipolar neuron and a example?
A
One axon, multiple dendrites. An example of this are motor neurons and interneurons.
24
Q
What is the structure of a bipolar neuron and a example?
A
One axon, one dendrite. An example of this is through sensory neurons (eye, ear, nose).
25
What is the structure of a pseudo-unipolar neuron and a example?
One axon splitting into two. These are general sensory neurons.
26
How is the resting membrane potential maintained at -70mv?
1) Potassium/Sodium pumps
2) Potassium leakage channels
3) Large anionic organic molecules
27
What is a nerve impulse?
Is an electrochemical signal transmitted along a neuron due to the movement of ions across the membrane.
28
What is an action potential?
It is a rapid change in membrane potential that allows neurons to transmit electrical signals. It occurs when a neuron is stimulated beyond its threshold potential (-55mV), causing ion channels to open and an electrical impulse to propagate along the axon. This process follows an all-or-nothing response.
29
How does a nerve impulse travel across a synapse?
1) Neurotransmitters stored in vesicles.
2) When a nerve impulse reaches the axon terminal, voltage-gated calcium channels open.
3) Calcium ions rapidly diffuse into the presynaptic axon terminal and stimulate the formation of synaptic vesicles.
4) Synaptic vessels containing neurotransmitters are relessed into the synaptic cleft via exocytosis.
5) The neurotransmitters diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane.
30
What are the 5 key steps in a action potential?
1) Resting Potential
2) Depolarisation
3) Repolarisation
4) Hyperpolarisation (Refractory Period)
5) Resting Potential Restores
31
What happens in resting potential?
- The membrane potential is a -70mV
- Na⁺ (sodium) is outside the neuron, K⁺ (potassium) is inside.
- The neuron is at rest.
- The sodium-potassium pump actively transports 3 Na⁺ out and 2 K⁺ in, maintaining a negative charge inside the neuron.
- The inside of the neuron is more negative than the outside.
32
What happens in depolarisation?
- If a stimulus reaches threshold (-55mV), voltage-gated Na⁺ channels open.
- Na⁺ (sodium ions) rapidly diffuse into the cell )due to the concentration gradient) till the membrane potential reaches +40mV.
- The inside becomes more positive.
33
What happens in repolarisation?
- When the membrane potential reaches +40mV, the voltage-gated Na⁺ channels close, stopping Na⁺ entry.
- Voltage-gated K⁺ channels open, allowing K⁺ to exit the neuron.
- The inside becomes negative again as K⁺ leaves.
34
What happens in hyperpolarisation?
- K⁺ channels close slowly, causing too much K⁺ to leave.
- The neuron becomes more negative than its resting potential (-80mV).
- The neuron cannot fire another action potential at this time (refractory period).
35
What happens when resting potential restores?
- The sodium-potassium pump restores Na⁺ and K⁺ levels.
- The neuron is ready for another action potential.
36
What happens in myelinated fibres?
Impulse "jumps" between Nodes of Ranvier via saltatory conduction, making transmission much faster.
37
What happens in unmyelinated fibres?
Impulse travels continuously along the axon, resulting in slower conduction.
38
What are the effects of a stimulus?
Enhance neurotransmitter activity such as caffeine.
39
What are the effects of depressants?
Slow down nerve impulse transmission such as anaesthetics.
40
What are the effects of nerve agents?
Cause excessive nerve stimulation, leading to muscle paralysis.
41
What is a receptor?
A receptor is a structure that detects changes in the body’s internal or external environment.
42
What are the different types of receptors?
1) Thermoreceptors
2) Osmoreceptors
3) Chemoreceptors
4) Touch Receptors
5) Pain Receptors
43
What is the function of thermoreceptors and where are they found?
They detect temperature changes and are found in the skin and the hypothalamus.
44
What is the function of osmoreceptors and where are they found?
They detect changes in water concentration and are found in the hypothalamus.
45
What is the function of chemoreceptors and where are they found?
They detect chemical changes (pH, oxygen levels) and are found in the blood vessels, nose and mouth.
46
What is the function of touch receptors and where are they found?
They detect physical touch, pressure and vibration and are found in the skin and hair follicles.
47
What is the function of pain receptors and where are they found?
They detect tissue damage and are found in the skin and organs (except the brain).
48
What is a reflex?
A reflex is a rapid, automatic response to a stimulus that protects the body or maintains homeostasis.
49
What are the 4 properties of reflexes?
1) Stimulus required – Reflexes are triggered by external/internal stimuli.
2) Involuntary – No conscious control is involved.
3) Rapid – Only a small number of neurons are involved.
4) Stereotyped – The same response occurs every time.
50
What are the basic components of a reflex arc?
1) Receptor - Detects stimulus and initiates impulse.
2) Sensory neuron - Carries impulse from receptor to spinal cord.
3) Interneuron (if present) - Processes signal and relays it.
4) Motor neuron - Carries impulse to an effector.
5) Effector - Responds to stimulus (e.g., muscle contracts).
51
What are the steps of a reflex arc?
1) Receptor detects a stimulus.
2) Sensory neuron transmits nerve impulse to the spinal cord.
3) Impulse passes through at least one synapse in the spinal cord (either directly to a motor neuron or via an interneuron).
4) Motor neuron carries the impulse to the effector.
5) Effector carries out the response.
52
What are the different types of reflexes tested in a clinical setting?
1) Knee-Jerk Reflex - Tapping the patellar tendon causes a rapid leg extension.
2) Heel Reflex - Applying pressure to the sole of the foot causes the toes to curl.
3) Eye Reflex (Blink Reflex) - Objects approaching the eye cause automatic blinking for protection.
53
What are the characteristics of the nervous system?
Nature of the message - Through electrical impulses and neurotransmitters.
Transmission - Along neurons.
Effect - Local and specific.
Speed of response - Fast (milliseconds).
Duration of response - Short-lived.
54
What are the characteristics of the endocrine system?
Nature of the message - Through chemical hormones.
Transmission - Through blood.
Effect - Widespread.
Speed of response - Slow (seconds to days)
Duration of response - Long-lasting.
55
What are the overlapping factors of the nervous and endocrine systems?
- Neurotransmitters and hormones can have similar effects (noradrenaline functions as both).
- The hypothalamus connects both systems by regulating pituitary hormone release.
- Both systems maintain homeostasis (e.g., controlling heart rate, digestion, and stress responses).
56
What is the role of the CNS in the human body?
The CNS (Brain + Spinal Cord) processes incoming messages and initiates responses to coordinate bodily functions.
57
What are key structures of the CNS?
- Cerebrum
- Cerebral cortex
- Corpus callosum
- Basal ganglia
- Hypothalamus
- Medulla oblongata
- Cerebellum
58
What is the structure of the cerebrum?
Outersurface is the cerebral cortex and is composed of grey matter and the inner surface is composed of white matter.
59
What is the cerebrum's function?
Responsible for higher order thinking, language, memory, movement and sensory movement.
60
What is the structure of the cerebral cortex?
It is composedof grey matter and is divided into 4 main lobes:
1) Frontal lobe
2) Parietal lobe
3) Occipital lobe
4) Temporal lobe
61
What is the frontal lobe responsible for?
Higher order thinking such as:
- Thinking and decision-making
- Planning and problem-solving
- Voluntary movement (motor cortex)
- Speech production
- Emotions and personality
62
What is the parietal lobe responsible for?
Perception of sensory information such as
- Processing touch, pressure, pain, and temperature (somatosensory cortex)
- Spatial awareness and navigation
63
What is the occipital lobe responsible for?
Visual processing such as (shape, color, motion).
64
What is the temporal lobe responsible for?
Processing sensory information such as:
- Hearing and understanding sounds
- Language comprehension
65
What is the structure of the corpus callosum?
Composed of large bundles of white matter known as transverse fibres.
66
What is the function of the corpus callosum?
Connects the left and right hemispheres of the brain.
67
What is the structure of the basal ganglia?
Grey matter deep within the cerebrum.
68
What is the function of the basal ganglia?
Responsible for intitiating movement and inhibiting unwanted movement.
69
What is the structure of the hypothalamus?
Located deep within the brain below the thalamus and above the pituitary gland.
70
What is the function of the hypothalamus?
Primary function is maintaining homeostasis.
71
What is the structure of the medulla oblongata?
Lowest part of the brain stem.
72
What is the function of the medulla oblongata?
- Cardiac centre
- Respiratory centre
- Vasmotor centre
- Also responsible for certain reflexes like coughing and sneezing.
73
What is the structure of the cerebellum?
It is located at the back of the brain and folded into parallel ridges with the outer section being grey matter and the inside section being white matter.
74
What is the function of the cerebellum?
Controls balance and coordination.
75
What is the main role of the PNS?
The PNS connects the CNS to the rest of the body, carrying signals to and from the brain and spinal cord.
76
What are the 2 main stuctures in the PNS?
1) Cranial Nerves (12 pairs)
2) Spinal Nerves (31 pairs)
77
What is the function of the cranial nerves?
Carry sensory and motor signals directly to/from the brain. Example: Optic nerve (vision).
78
What is the function of the spinal nerves?
Carry sensory and motor signals to/from the spinal cord.
79
What are the 2 divisions of the PNS?
1) Afferent (Sensory) Division
2) Efferent (Motor) Division
80
What is the afferent (sensory) division?
Carries sensory signals to the CNS. It is composed of sensory (afferent) neurons, which detect stimuli and send signals to the brain and spinal cord.
81
What are the different types of sensory neurons?
1) Somatic Sensory Neurons – Transmit information from skin, muscles, and joints.
2) Visceral Sensory Neurons – Transmit information from internal organs.
82
What is the efferent (motor) division?
Carries motor signals from the CNS to muscles/glands. It is composed of motor (efferent) neurons that transmit impulses to muscles and glands.
83
How is the efferent (motor) division subdivided into?
1) Somatic System
2) Autonomic System
84
What is the somatic system?
- Controls voluntary movements by transmitting signals to skeletal muscles.
- Controls the body's response to the external environment.
- Uses one nerve fibre to directly connect the CNS to the muscle (effector).
- Unmyelinated neurons
- Neurotransmitter: Acetylcholine (ACh).
85
What is the autonomic system?
- Controls involuntary functions by regulating the heart, glands, and smooth muscle.
- Uses two neurons (pre-ganglionic and post-ganglionic) that synapse in a ganglion.
- Myelinated neurons
- Neurotransmitters: Acetylcholine (ACh) or Noradrenaline (NA).
86
How is the autonomic system divided into?
1) Sympathetic
2) Parasympathetic
87
What is the sympathetic nervous system?
It is the bodys fight or flight response and it prepares the body for stress, danger, or high activity.
88
What are symptoms of the sympathetic nervous system in action?
- Increases heart rate and breathing rate.
- Dilates pupils and bronchioles.
- Inhibits digestion and saliva production.
- Stimulates glucose release from the liver.
- Release of adrenaline and noradrenaline.
- Constricts vessels.
89
What is the parasympathetic nervous system?
This is the bodys rest and digest response and returns the body to a state of rest and conserves energy.
90
What are symptoms of the parasympathetic nervous system in action?
- Decreases heart rate and breathing rate.
- Constricts pupils and bronchioles.
- Stimulates digestion and saliva production.
- Promotes glucose uptake by the liver.
