Alzheimer’s happens because:
Neurons in brain shrink or disappear.
Abnormal material builds up, neurofibrillary tangles inside neurons, amyloid plaques around remaining neurons.
Disrupts messages, damages connections between neurons -> death
Parkinson’s happens because:
Deficiency in neurotransmitter dopamine.
Caused by progressive degeneration of nerve cells in brain’s basal ganglia.
A nerve impulse is an electrochemical change:
- a change in electrical voltage
- is bought about by change in chemicals.
When the impulse reaches the axon terminal:
Activates the voltage-gated calcium ion channels, and so the calcium enters the cell at the pre-synaptic axon terminal following the concentration gradient.
This causes:
Synaptic vesicles to fuse with the membrane, which releases neurotransmitters by exocytosis.
These diffuse the gap, and bind to the next neuron’s receptors, and the process repeats.
Conduction along unmyelinated
maximum of 2 m/s
Conduction along myelinated
maximum of 140 m/s
Sensory areas
interprets impulses from receptors.
Motor areas
controls muscular movements.
Association areas
interprets information from senses and makes it useful, emotional processes.
Three track types in white matter:
- Connects various areas of the cortex within same hemisphere.
- Carries impulses between left and right hemispheres.
- Connects cortex to other parts of the brain/spinal cord.
Basal ganglia
- Grey matter deep inside cerebrum.
- Consists of nerve cell bodies associated with skeletal muscle control.
- Helps initiate desired movements and inhibiting unwanted movement.
Dura mater in spinal cord
not joined to bone, instead to a space containing fat, connective tissue and blood vessels to serve as padding and allows bending.
Mechanoreceptors
Senses pressure
Osmoreceptors
Detects solute concentrations in blood
Somatic sensory neurons
brings impulses from skin and muscles.
Visceral sensory neurons
brings impulses from internal organs.
Autonomic pathway:
- Goes across two neurons to an organ controlled by ANS.
- First neuron myelinated, second is unmyelinated.
- Has a ganglion.
- Sympathetic and parasympathetic nerves.
- Acetylcholine or noradrenaline neurotransmitters at effector.
Somatic pathway:
- Goes across one neuron to a skeletal muscle.
- Neuron is myelinated, no ganglion or synapse.
- Only acetylcholine.
- Either sympathetic or parasympathetic, not both.
Sympathetic neurotransmitter vs parasympathetic neurotransmitter
Parasympathetic is acetylcholine and sympathetic is noradrenaline.
Alter cell activity by:
- Activating certain genes in nucleus so that a particular enzyme or structural protein is produced.
- Changing the shape or structure of an enzyme so it is ‘off’ or ‘on’.
- Changing enzyme/structural protein production rate by changing transcription or translation rate during protein synthesis.
Explain why hyperpolarisation reduces the likelihood of a new action potential being created.
As the inside of the membrane is more negative than at resting potential, more sodium ions must enter in order for the potential difference to hit the threshold for an action potential to be created.
Describe the metabolic effects of growth hormone.
Stimulates the production of bone cells and bone tissue development.
Stimulates muscle growth through protein synthesis.
