Please enable JavaScript.
Coggle requires JavaScript to display documents.
Biopsychology - Coggle Diagram
Biopsychology
Structure and Function of Sensory, Relay, and Motor Neurons
Around 100 billion neurons in the human nervous system - 80% located in the brain - transmit signals electrically and chemically - provide the nervous system with its primary means of communication
Structure of a Neuron:
The cell body (soma) contains a nucleus which contains the genetic material of the cell - dendrites are branch like structures that protrude from the cell body and receive signals from other neurons or from sensory receptors - the axon carries the impulses away from the cell body - the axon is covered in a fatty layer called the myelin sheath that protects the axon and speeds up electrical transmissions - the myelin sheath is segmented by gaps called nodes of Ranvier that speed up transmission by forcing it to jump across gaps in the axon - at the end of the axon are terminal buttons that communicate with the next neuron in the chain - the gap in between is the synapse
Types of Neuron:
Sensory: found in sensory receptors like the eyes, ears, tongue, skin - carry nerve impulses from the PNS to the spinal cord and brain - signals translated into sensations like vision, hearing, taste and touch - allow for quick reflex actions - long dendrites and short axons
Relay: most common type of neuron - found in the brain and spinal cord (CNS) - connect sensory neurons to motor or other relay neurons - short dendrites and short axons
Motor: carry messages from the CNS and control muscle movements - release neurotransmitters that bind to receptors on the muscle to trigger a response resulting in a muscle movement - short dendrites and long axons
Reflex Arc:
PNS: sensory neuron - senses are triggered
TO
CNS: relay neuron - mental processes occur
TO
PNS: motor neuron - effector
How neurons function together:
- Stimulus is presented
- Sensory neuron send a message through the peripheral nervous system
- Message reaches the spinal cord and is passed on to a relay neuron in the central nervous system
- Message is then passed to a motor neuron or sent to the brain for further processing
- Motor neuron carries the message to an effector e.g. a muscle or gland
-
-
Localisation of Function in the Brain: the idea that specific functions have specific locations within the brain and so if that area is damaged the associated function is also damaged - brain divided into two symmetrical halves and the outer layer of the hemispheres is called the cerebral cortex
Auditory Centres: two primary auditory cortices (one in each hemisphere) - primary auditory cortex in both hemispheres receives information from both ears via two pathways - located in the temporal lobe - damages can cause partial or full hearing loss
Motor Centres: sends messages to the muscles via brain stem and spinal cord - responsible for generating voluntary motor movement - located at the back of the frontal lobe in both hemispheres - each control the movement for the opposite side of the body (contralateral) - damage results in loss of control of fine movements
Somatosensory Centres: sensations in the body - next to the motor cortex - where sensory information from the skin is represented - perceives touch - located at the front of the parietal lobe in both hemispheres - receives sensory information from the opposite side of the body
Visual Centres: one in each hemisphere - in the occipital lobe at the back of the brain - each eye sends information contralaterally - damage results in vison loss
Language Centres: left hemisphere
1. Broca's Area - responsible for speech production - located in the left frontal lobe - damage causes Broca's aphasia (slow, laborious and fluency lacking speech)
2. Wernicke's Area: responsible for understanding language - left temporal lobe - damage causes Wernicke's aphasia (produce nonsense words as part of speech content)
AO3: Strength - localisation is supported by case study evidence - Patient Tan - could only say the word 'tan' upon his death an autopsy was carried out and it was found he had a legion in a region of his brain (Broca's area) - concluded this region of brain was responsible for speech production - adds validity to the theory
AO3: Strength - further research from brain scans - Peterson et al - used brain scans to show that Wernicke's area was active during a listening task and Broca's was active for a reading task - objective evidence showing the theory - adds validity
A03: Weakness - contradictory evidence from animal studies - Lashley - removed 10-50% of a rats cortex when learning a maze and found no area was more important that another with learning the maze - suggests functions are not localised but more distributed across the entire brain in a holistic way - reduces the validity of the theory
AO3: Weakness - evidence from plasticity studies don't support localisation - brain able to recover after damage - study on a patient who damaged left hemisphere and developed the ability to speak in the right hemisphere - suggests functions aren't restricted to specific brain regions and the brain can redistribute tasks to other areas
-
Process of Synaptic Transmission; Neurotransmitters, Excitation and Inhibition
Synaptic Transmission:
1. The nerve impulse (action potential) travels down the axon of the pre-synaptic neuron
2. When it reaches the end of the axon, chemical neurotransmitters are released from vesicles within the pre-synaptic neuron
3. These diffuse across the synapse (gap between neurons)
4. The neurotransmitters then bind to receptors on the post-synaptic neuron
5. This stimulates the post-synaptic neuron to transmit a nerve impulse (action potential) down its axon, to the next neuron
6. The neurotransmitters left in the pre-synaptic gap are then deactivated by being reabsorbed into the pre-synaptic neuron or are broken down by enzymes in the synapse
Excitation and Inhibition:
Neurotransmitters have either an excitatory (on-switch) or inhibitory (off-switch) effect on the neighbouring neuron
Inhibition: e.g. serotonin - causes inhibition in the receiving neuron resulting in the neuron becoming more negatively charged and less likely to fire - message is likely stopped at the post-synaptic neuron and is called a inhibitory synapse - like the brake
Excitation: e.g. dopamine - causes excitation in the receiving neuron by increasing its positive charge and making it more likely to fire - message is likely continued and is called an excitatory synapse - like the accelerator
Summation: when a neuron received both inhibitory and excitatory neurotransmitters at the same time - likelihood of the cell firing is determined by adding up the excitatory and inhibitory synaptic input (summation) - if the net effect is inhibitory then the neuron is less likely to fire and if the net effect is excitatory the neuron is more likely to fire
-
-
-
-