Biopsychology (AQA AS Level Psychology)

The nervous system

The nervous system is split into 2 sub-components: The central (brain and spinal cord) and peripheral (CNS and PNS). The PNS is split into the Somatic NS (voluntary control of skeletal muscles) and autonomic NS (involuntary responses). The autonomic nervous system is split into the sympathetic NS (fight or flight) and the parasympathetic NS (rest and digest).

Types of neuron

Sensory neurons carry nerve impulses from receptors to the CNS (spinal cord and brain). They have a cell body in the middle of their myelinated axon.

Relay neurones carry impulses within the CNS, allowing sensory and motor neurons to communicate. They have an un-myelinated short axon with many dendrites and axon terminals.

Motor neurones carry impulses from CNS to effector organs (e.g. muscles). The cell body is at the end of the myelinated axon.

Synaptic transmission

The action potential reaches the axon terminal of the presynaptic neuron, this causes neurotransmitters to form in vesicles. The vesicles move to the presynaptic membrane and release neurotransmitters into the synapse. The neurotransmitters diffuse across the synaptic cleft and bind with receptors on the postsynaptic neurone. The net excitatory/inhibitory input is calculated (summation) and when there is an EPSP (excitatory postsynaptic potential), an action potential is triggered. The re-uptake mechanism causes unbound neurotransmitters to be taken up by the presynaptic neurone.

The endocrine system

The endocrine system is a network of glands that produce and secrete hormones into the bloodstream.
The major glands include the pituitary gland (“master” gland which produces hormones that control other glands), adrenal glands (produce adrenaline and cortisol) and reproductive organs: ovaries (oestrogen and progesterone) and testes (testosterone).

Fight or flight response

An acute stressor is detected. The amygdala associates the sensory information with emotions (e.g. fear) and sends a signal to the hypothalamus to trigger the sympathetic nervous system which causes the adrenal medulla to release adrenaline into the bloodstream. This increases heart rate, opens airways wider, dilates pupils, stops digestion etc. This is flight or fight.
The parasympathetic nervous system returns the body to normal once the threat has passed (rest and digest).

Chronic stress response

H: The hypothalamus releases CRH which causes the
P: pituitary gland to release ACTH which travels to the
A: adrenal cortex to release cortisol.

Cortisol increases blood sugar to maintain energy levels, elevates blood pressure putting strain on the heart and affects sleep and digestion.

Evaluate fight or flight

- Is not a universal explanation because ignores the gender differences. Females experience tend and befriend (care for children and group together with other females). Fight or flight is an androcentric explanation (research was only conducted on male rats but have extended the assumptions onto females) that ignores gender differences.

- Not a full explanation because doesn’t consider freeze as an option. Gray argues that prior to fight or flight most animals (including humans) freeze to be alert and assess the situation before a fight or flight is chosen.