Biopsych

the nervous system is split into

central nervous system (CNS) and peripheral nervous system (PNS)

compare the function of CNS and PNS

CNS is the main control system for functions including conscious psychological processes whereas PNS transmits information between the CNS and external world. 

CNS consists of

brain and spinal chord

PNS consists of

somatic and autonomic

autonomic nervous system is split into

sympathetic and parasympathetic nervous system

CNS: the brain

• higher psychological processes

• cerebral cortex is the outer layer made up of highly folded grey matter

• divided into 2 symmetrical hemispheres the left and right

• 4 distinct lobes: frontal, parietal, occipital, temporal

• Under the cerebral cortex is the more primitive area and is concerned with vital functioning and instinctive behaviour

function of the cerebral cortex

• higher cognitive (conscious thought)

• emotional, sensory (5 senses)

• motor (movement) functions

left hemisphere of the brain

for language, the ‘rational’ half of the brain, associated with analytical thinking and logical abilities

right hemisphere of the brain

involved with musical and artistic abilities

CNS: spinal chord

• bundle of nerves, which runs from your brain along a canal in your backbone

• sends nerve signals from the brain to the body, and from the body to the brain

• also involved in reflex actions, such as the startle response

• brain is connected to the spinal cord by the brain stem.

somatic nervous system

• responsible for voluntary movement that you do on purpose (e.g. walking).

• controls the voluntary movement of skeletal muscles eg biceps

• consists of the nerves that carry messages to the eyes, ears, skeletal muscles.

• transmits information between the central nervous system and the senses

• under conscious control

autonomic nervous system

• controls involuntary movement

• transmits information from the CNS to the internal organs and from non-skeletal muscles, eg cardiac muscle

differences between SNS and ANS

• SNS voluntary ANS involuntary

• SNS functions include posture and movement; ANS functions include secretion and control of metabolism

• SNS –in vertebrates - includes excitatory neurotransmitters ANS – in vertebrates has both excitatory & inhibitory neurotransmitters

sympathetic nervous system

• activated in situations requiring arousal and energy

• prepares the body for “fight or flight” responses during stressful situations

• prepares the body’s resources for immediate action

• produces increased heart and respiratory rate, increasing blood flow to the muscles and pupil dilation to help the body to survive.

parasympathetic nervous system

• activated soon after the threat of danger has passed

• opposite effect of the SNS and allows for the body to return to homeostasis

• person’s heart and respiratory rate decrease to normal levels and blood flow decreases, pupils return to normal size

• vital to conserve energy and not to become exhausted

how neurones collect info

• through the dendrites and sends info to the cell body

• cell body weighs up the info received and makes a binary decision to fire its own electrical charge (action potential)

• action potential will travel along the axon to the axon terminal

types of neurone

sensory, motor and relay

neurotransmitters

chemicals that pass from one neuron to another to pass the signal being transmitted

synaptic transmission

• Electrical impulses are passed through the axon of a neuron to the axon terminal causing depolarisation of the presynaptic neuron. but cannot go through the synaptic cleft.

• Instead, electrical impulse causes calcium channels to open, and positively charged calcium rushes into the cell. This

• triggers vesicles with neurotransmitters to move towards the membrane at the axon terminal and release neurotransmitters into the synapse. They then diffuse across the synapse

• They then bind to the receptors on the post-synaptic neuron. which triggers the a signal in the post synaptic neuron.

• Neurotransmitters can have an excitatory effect on the receiving neuron or an inhibitory effect (making them less likely to fire).

excitatory effect on neurones

making them more likely to fire an impulse

inhibitory effect on neurones

making them less likely to fire an impulse

summation

• the charge results in a net effect on the post synaptic neuron

• membrane has to reach over a certain voltage (membrane potential) in order to fire.

• If the net effect is excitatory (more positive than negative) the neuron will be more likely to fire

• if inhibitory (more negative than positive charge) then neuron is less likely to fire.

what happens once the neurotransmitters have bound to receptor sites

• a signal has been sent in the post synaptic neuron, the

• neurotransmitters unbind from the receptors.

• Then either the neurotransmitters travel back into the presynaptic neuron via a reuptake channel, and get repackaged back into vesicles to be used again or are are broken down by enzymes.

sensory neurones

• located in the PNS

• respond to stimulation in sensory receptors for all senses (vision, hearing, smell, taste, touch).

• send signals to the CNS about this sensory experience.

• Most have long dendrites and short axons

• carry signals away from the organ to the brain and spinal cord (afferent).

motor neurones

• cells in the PNS that send messages from the brain and the spinal cord to the muscles and glands (efferent)

• usually have long axons and short dendrites

• help to produce a movement or a response

relay neurones (interneurons)

• form connections between other neurons

• send signals to other relay neurons, or form links between sensory and motor neurons

• All neurons in the CNS are relay neurons, and there are over 100 billion relay neuron

reflex arc eg when you touch a hot pan

• receptors in your skin sense the stimulus (the hot pan)

• Sensory neurons send an electrical impulse towards the CNS from the dendrites, along the axon, to the axon terminal

• In the CNS, a relay neuron carries this signal to a motor neuron

• A motor neuron now transmits the signal from the CNS to the muscle

• you are now able to move your hand away.

function of endocrine system

network of glands across the body that secret hormones (chemical messengers) to regulate vital functions

pituitary gland hormones

Oxytocin, Thyroid Stimulation Hormone (TSH) , ACTH

pituitary gland action

‘Master gland’ as it controls all other glands, TSH signals action in the thyroid, Adrenocorticotrophic Hormone (ACTH) signals action in the adrenal glands

thyroid gland hormone

thyroxine

thyroid gland action

Primarily involved with the regulation of metabolism, such as the conversion of food into energy for the muscles

parathyroid gland hormone

parathyroid hormone (PTH)

parathyroid gland action

acts to increase the concentration of calcium in the blood from kidneys and bone.

pancreas hormone

insulin

pancreas gland action

Promotes the absorption of glucose from the blood into fat, liver and skeletal muscle cells. Insulin lowers blood glucose levels.

adrenal gland hormones

Adrenaline & Noradrenaline

adrenal glands action

Responsible for reacting to threat via the fight or flight response eg increased heart rate

ovaries hormones

Oestrogen and progesterone

ovaries gland action

Responsible for the development and regulation of the female reproductive system and secondary sex characteristics.

testes hormone

testosterone

testes action

key role in the development of male reproductive system such as the testes and prostate, as well as promoting secondary sexual characteristics eg increase muscle/ bone mass, growth of body hair

pineal gland hormone

melatonin

pineal gland action

regulates the sleep-wake cycle

fight or flight response

• a threat is detected by sensors in the eye via hypothalamus and our sympathetic nervous system is activated at the same time as endocrine

• hypothalamus signals to the pituitary gland to activate endocrine system

• pituitary releases ACTH which travels through blood stream and is detected by cells in the adrenal gland

• which stimulates adrenaline to be released

• triggers lungs to increase breathing rate, pupils dilate for increased vision, stomach diverts blood to muscles for strength, heart rate increases to pump blood to vital organs

parasympathetic response to fight or flight

• After a few minutes, the parasympathetic branch of the ANS is activated, and the body returns to normal by establishing homeostasis.

• Heart rate and respiratory rates decrease, adrenaline secretion slows down, the feeling of butterflies subside and sweating stops.

fight or flight first studied by Walter Cannon ignoring freeze AO3

• limitation of his conclusion is he didn’t explain why our responses are not limited to fighting or fleeing as some have a freeze response

• Gray suggests that the first response to danger is to avoid confrontation altogether in the freeze response

• during freeze response animals and humans are hyper-vigilant while they appraise the situation to decide thee best course of action for that threat

• fight or flight by Cannon then may not be a full explanation, limiting usefulness

evidence supporting fight or flight first studied by Walter Cannon ignoring freeze AO3

Gray suggests that the first response to danger is to avoid confrontation altogether in the freeze response

limitation of Cannon’s research is it has beta and gender bias AO3

• research conducted in 1915 on male animals and no researchers undertook detailed female studies till 2000

• recent research suggests females adopt a “tend and befriend” response in stressful/ dangerous situations

• Taylor et al foound wowmen are morre likely to protect their offspring