Nervous system

Question 1

What is the stimulus-response principle (5)

Answer 1

e.g. the cough reflex

1. Stimulus triggers peripheral sensory neurone
2. Sensory neurone travels to the brain stem
3. in the brain stem, the central nervous system processes inputs and makes a decision on which efferent pathways to activate
4. information is sent out through axons in different efferent fibres to organs
5. reflex arc mediates the response to the stimulus and coordinates the activity of specific cells to achieve the outcome.

Question 2

What allows the electrical excitability of cells (4)

Answer 2

1. Excitability refers to a cell’s ability to respond to stimuli and generate electrical signals.
2. Ion channel permeabilities are responsible for the changes in membrane potential that lead to electrical signals.
3. Excitatory Post-Synaptic Potentials (EPSP): Lead to depolarization (more likely to generate action potentials).
4. Inhibitory Post-Synaptic Potentials (IPSP): Lead to hyperpolarization (less likely to generate action potentials).

Question 3

What is the electrical excitability of cells principle (6)

Answer 3

1. Neurones have a cell body containing machinery for electrogenic processes that prime for excitability by establishing a hyperpolarised resting membrane voltage and low levels of intracellular calcium
2. Dendrites provide surfaces for synaptic inputs that receive inhibitory and excitatory signals generated by ligand-operated channels. that determine the post-synaptic excitability, causing a change in membrane voltage.
3. The effects of Excitatory Post Synaptic Potentials (EPSP) are depolarising.
4. Action potentials are a conducting/propagating **depolarising (+) then repolarising (-) “wave” that is spread along the axon by voltage-operated channels VOC for Na+ & K+.
5. At the synaptic terminal, depolarisation opens voltage-operated channels VOC for Ca; then, Ca-dependent vesicle fusion and transmitter release into the synaptic cleft occur.
6. The result is chemical transmission **to a postsynaptic cell, where receptors driving ligand-operated channels (LOC) exert excitation (depolarization) of the follower cells’ membrane voltage, which leads to changes in intracellular calcium and cellular responses of muscle, gland, or nerve

Question 4

What is the chemical signalling types principle (4)

Answer 4

1. the cell body has a membrane with pumps (sodium-potassium ATPase) which establishes ion gradients and has leakage potassium channels
2. The cell establishes electrical excitability, a hyperpolarised resting membrane potential and a very low intracellular calcium level
3. the cell body has synaptic boutons on its dendrites, which are the location for inputs from different cells
4. axon release releasing action potential in the following cell so membrane voltage goes down, becoming

Question 5

What are the central (CNS) components

Answer 5

The Central Nervous System (CNS) is composed of two main parts: the brain and the spinal cord. Together, these structures serve as the primary control centre for the body, managing sensory information, motor responses, and various cognitive processes.

Question 6

What are the components of the brain and their functions (6)

Answer 6

1. Cerebrum: divided into two hemispheres (left and right) and further subdivided into lobes (frontal, parietal, temporal, occipital).
2. Cerebellum: Located under the cerebrum at the back of the brain, responsible for coordination and balance.
3. Brainstem: Includes the midbrain, pons, and medulla oblongata, and connects the brain to the spinal cord.
4. Diencephalon: Contains structures like the thalamus and hypothalamus, which are involved in sensory processing and homeostasis.
5. Limbic system: Includes structures such as the amygdala and hippocampus, playing a key role in emotions, memory, and motivation.
6. Basal ganglia: Involved in regulating motor control, behaviours, and emotions.

Question 7

What are the components of the spinal cord and their functions (3)

Answer 7

1. The spinal cord is composed of nerve fibres that run from the base of the brain to the lower back, enclosed within the vertebral column.
2. The spinal cord is divided into segments corresponding to the vertebrae: cervical, thoracic, lumbar, sacral, and coccygeal.
3. It consists of grey matter (cell bodies, dendrites) on the inside and white matter (myelinated axons) on the outside.

Question 8

What are the functions of the spinal cord (4)

Answer 8

1. The spinal cord carries sensory information from the body to the brain (afferent pathways).
2. It also transmits motor commands from the brain to muscles and glands (efferent pathways).
3. The spinal cord mediates reflex actions, allowing for quick, automatic responses to stimuli (e.g., withdrawal from a painful stimulus) without requiring input from the brain.
4. Controls involuntary processes such as bladder control, blood pressure regulation, and digestive reflexes through the autonomic nervous system

Question 9

What are the peripheral (PNS) nervous system components, structure and functions (5)

Answer 9

Divided into two major parts:

1. Somatic Nervous System (SNS) - **controls voluntary movements by innervating skeletal muscles and carries sensory information from receptors in the skin, muscles, and joints to the CNS.
2. Autonomic Nervous System (ANS) - regulates involuntary functions such as heart rate, digestion, and respiratory rate. Further subdivided into:
3. Sympathetic Nervous System - “fight or flight”
4. Parasympathetic Nervous System - “rest and digest”
5. Enteric Nervous System - **Manages gastrointestinal functions and is sometimes referred to as the “second brain.”

Question 10

What is the PNS made up of (4)

Answer 10

1. The PNS is made up of nerves, which are bundles of axons (nerve fibres) that transmit electrical impulses between the CNS and the rest of the body. There are two types of nerves in the PNS:
2. Cranial nerves (12 pairs): These nerves originate directly from the brain and innervate the head, neck, and some internal organs.
3. Spinal nerves (31 pairs): These nerves emerge from the spinal cord and are responsible for communication between the CNS and different parts of the body below the head.
4. Ganglia are clusters of neuron cell bodies located outside the CNS. These serve as relay points where nerve signals can be transmitted or modulated before reaching their final destination.

Question 11

What are the endocrine system components (9)

Answer 11

Components:

1. Hypothalamus - hormone secretion, homeostasis, produce releasing and inhibiting hormones
2. Pituitary gland - GH, TSH, ACTH, Prolactin, FSH, LH, ADH, Oxytocin
3. Thyroid gland - T3, T4, heart rate, muscle function, brain development, calcitonin
4. Parathyroid glands - PTH
5. Adrenal glands - regulate metabolism, control blood pressure, sex hormones, adrenaline, noradrenaline
6. Pancreas - insulin, glucagon
7. Pineal Gland - melatonin
8. Gonads - estrogen, progesterone, testosterone
9. Thymus gland - development of T-cells

Question 12

What are the functions of the endocrine system (7)

Answer 12

1. Regulate metabolism
2. growth and development
3. maintaining homeostasis
4. reproductive functions
5. stress response
6. regulating sleep cycles
7. immune system regulation