Biopsychology

synaptic transmission

The way that neurons communicate with each other. It involves a message being passed chemically between neurons

Steps of synaptic transmission

• an electrical signal reaches the end of the presynaptic neuron and it arrives at the terminal button to be passed onto the postsynaptic neuron

• the electrical signal causes the vesicles to release the neurotransmitters they are carrying into the synaptic cleft

• the NT crosses the synaptic cleft and makes its way to the postsynaptic neuron. It can only enter the postsynaptic neuron if it fits into the receptor site

• The NT enters the receptor site and causes an electrical message down the postsynaptic neuron, ready to be passed on to the next one. Any NTs that are left in the synaptic cleft might be broken down or reabsorbed by the presynaptic neuron (reuptake channels) so it can be used again

excitatory neurotransmitter

binds to the receptor sites and increases the chances of the postsynaptic neuron continuing the message to the next neuron as it makes it more likely to fire. It creates a positive charge

inhibitory neurotransmitter

binds to the receptor sites and decreases the chances of the postsynaptic neuron continuing the message to the next neuron as it makes it less likely to fire. It creates a negative charge

summation

A process which decides whether a post-synaptic neuron will fire. This happens by weighing up the amount of inhibitory neurons compared to excitatory neurons

sensory neuron

• Carry messages from the PNS to the CNS

• long dendrites, short axons

relay neuron

• connect the sensory neurons to the motor or other relay neurons

• short dendrites, short axons

motor neuron

• connect the CNS to the effectors such as muscles and glands

• short dendrites, long axons

How neurons communicate with each other

• sensory neuron sends the message to the relay neurons in the spine

• the relay neuron receives the message from the sensory neuron and passes it onto the motor neuron

• the motor neuron receives the message from the relay neuron and communicates with the muscle to move

function of the cell body

protects nucleus

function of the nucleus

contains DNA

function of dendrites

receive electrical signals from neurons

function of myelin sheath

protects axon and speeds up electrical signals

function of axon

carries the message through the neuron

node of ranvier

gaps between the myelin sheath that speed up electrical signal

terminal button

communicates to a nearby neuron

the nervous system

a specialised network of cells in the body that have two main functions: to collect, process and respond to info in the environment and to co-ordinate the organs in the body

central nervous system

made up of the brain and spinal cord

the spinal cord

a long structure running down our back. it carries incoming and outgoing messages between the brain and the body

brain

all decision making takes place here. at the base of the brain is the brain stem, which controls basic function

peripheral nervous system

recieves and sends messages to the CNS. it’s divided into the autonomic and somatic nervous system

somatic nervous system

we have some control over this system. It controls our movement. We don’t control the reflex part of our SNS

autonomic nervous system

we have no control over this system. it coordinates important functions such as breathing, HR and digestion. It is divided into the sympathetic division and parasympathetic division

sympathetic division

Controls fight or flight

parasympathetic division

controls rest and digest

What happens to the body during sympathetic action?

• heart rate increases

• salivation stops

• gut action stops

• pupils dilate

• rectum contracts

What happens to the body during parasympathetic action?

• heart rate decreases

• salivation resumes

• gut action resumes

• pupils constrict

• rectum relaxes

fight or flight

immediate physiological response of an animal when in danger. The body becomes physically ready to fight the threat or run away from it

Process of activation of fight or flight

• hypothalamus identifies threatening event and tells the parasympathetic division of the ANS to act

• ANS changes from normal resting state to a state of arousal. This releases adrenaline into the bloodstream

• physiological changes, such as increased heart rate, occur. These changes help to confront the threat or run away

• the ANS changes from the state of arousal to resting

endocrine system

a collection of glands that produce hormones which regulate our metabolism, growth, sleep etc.

Adrenal cortex

• produces cortisol

• controls cardiovascular and anti-inflammatory functions

Adrenal medulla

• produces adrenaline and non adrenaline

• prepares body for fight or flight

Thyroid

• produces thyroxine

• controls heart rate and metabolic rate

prancreas

• produces insulin and glucagon

• stimulates the release and absorption of glucose

pituitary gland

• controls hormone secretion in other glands

hypothalamus

• controls the functioning of the pituitary gland

testes

• produces testosterone

• regulates male secondary sex characteristics

ovaries

• produces oestrogen

• regulates female secondary sex characteristics

localisation of function

the idea that different areas of the brain are responsible for different behaviours, processes or activities

motor area

• frontal lobe

• controls voluntary movement in the opposite sided of the body

somatosensory area

• parietal lobe

• Where sensory information is represented

visual area

• occipital lobe

• each eye sends info from the right visual field to the left cortex and vise versa

auditory area

• temporal lobe

• analyses speech-based information

• both hemispheres

broca’s area

• frontal lobe

• small area in the left frontal lobe responsible for speech production

wernicke’s area

• temporal lobe

• region in the left temporal lobe being responsible for language and understanding

plasticity

the brains’s tendency to change and adapt (functionally and physically) as a result of experiences and new learning

Why do adults have less synaptic connections?

As we age, we “delete” rarely used connections and strengthen frequently used ones- this is known as synaptic pruning

Maguire’s research on plasticity

• she studied the brains of taxi driver's and found significantly more volume of grey matter in the posterior hippocampus than the matched control group. This part of the brain is associated with the development of spatial and navigational skills. London cabbies have to complete and test of their recall of different streets and routes. This experience alters their brain structures.

functional recovery

• a type of plasticity whereafter trauma, the brain redistributes from damaged areas to undamaged areas. This usually happens quickly after trauma and slows down after a few weeks/months

What happens in brain recovery?

1. axonal sprouting - the formation of new synaptic connections close to the area of damage

2. neuronal unmasking - secondary neural pathways that are dormant become activated to recover a lost connection

3. denervation super sensitivity - axons that do a similar job to the connections that were lost become further aroused to compensate for the lost one. This can lead to oversensitivity of messages

4. recruitment of homologous areas - the lost functions are recovered by the same area on the opposite side of the brain