Biopsychology Flashcards
Nervous system’s two main functions:
-To collect, process and respond to information in the environment.
-To co-ordinate the working of different organs and cells in the body.
Two sub-systems of the nervous system:
Central nervous system
Peripheral nervous system
Central nervous system, the brain:
The centre of all conscious awareness. Cerebral cortex distinguishes our higher mental functions from those of animals.
Central nervous system, the spinal cord:
An extension of the brain. Responsible for reflex actions.
Peripheral system is sub-divided into:
Autonomic nervous system- governs vital functions of the body.
Somatic nervous system- Controls muscle movement and receives information from sensory receptors.
Gland:
An organ in the body that synthesises substances such as hormones.
Endocrine system:
One of the body’s major information systems that instructs glands to release hormones directly into the bloodstream. These hormones are carried towards target organs in the body.
Hormones:
Chemical substances that circulate the bloodstream and only affects target organs. They are produced in large quantities but disappear quickpy.
Localisation of function:
The theory that different areas of the brain are responsible for different behaviours, processes or activities.
Motor area:
A region of the frontal lobe involved in regulating movement.
Somatosensory area:
An area of the parietal lobe that processes sensory information such as touch.
Visual area:
A part of the occipital lobe that receives and processes visual information.
Auditory area:
Located in the temporal lobe and concerned with the analysis of speech-based information.
Broca’s area:
An area of the frontal lobe of the brain in the left hemisphere (in most people) responsible for speech production.
Wernicke’s area:
An area of the temporal lobe (encircling the auditory cortex) in the left hemisphere (in most people) responsible for language comprehension.
Lateralisation:
The brain is divided into two symmetrical halves called left and right hemispheres, some of our physical and psychological functions are controlled or dominated by a particular hemisphere.
The four lobes:
The frontal lobe, the parietal lobe, the occipital lobe and the temporal lobes.
The frontal lobe:
At the back is the motor area which controls voluntary movement in the opposite side of the body. Damage can result in loss of control over fine movements.
Parietal lobe:
At the front is the somatosensory area which is separated from the motor area by a ‘valley’ called the central sulcus. The somatosensory area is where sensory information from the skin is represented.
Occipital lobe:
At the back of the brain is the visual area. Each eye sends information from the right visual field to the left visual cortex and vice-versa. Damage to the left hemisphere can produce blindness in the right visual field of both eyes.
Temporal lobes:
Houses the auditory area, which analyses speech-based information, damage may cause hearing loss.
Lateralisation
Evaluation- Brain scan evidence of localisation.
Peterson et al (1988) used brain scans to demonstrate how Wernicke’s area was active during a listening task and Broca’s area was active during a reading task, suggesting these areas have different functions.
Tulving et al (1994) showed that semantic and episodic memories reside in different parts of the prefrontal cortex.
Lateralisation
Evaluation- Neurosurgical evidence.
The practice of surgically removing/destroying areas of the brain to control aspects of behaviour developed in 1950s. Walter Freeman developed the lobotomy which severed connections in the frontal lobe attempting to control aggressive behaviour.
Neurosurgery is still used today in some extreme cases of OCD and depression.
Lateralisation
Dougherty et al (2002)
Reported on 44 OCD patients who had undergone cingulotomy- a neurosurgical procedure that involves lesioning of the cingulate gyrus. At post-surgical follow up after 32 weeks a third had met the criteria for successful response to the surgery and 14% for partial response. The success of procedures like this strongly indicates that symptoms and behaviours associated with serious mental disorders are localised.
Case of Phineas Gage.
Working on a railroad in 1848, 25 yr old Phineas gage was going to blast a section of rock with explosives to create a new rail line. Gage dropped his tamping iron on the rick cause the explosive to ignite. The explosion hurled a meter length rod through his left cheek, passing his left eye and exiting his skull taking a portion of his brain with it- most of his left frontal lobe.
Gage survived but his personality changed from calm and reserved to quick-tempered and rude.
Lateralisation
Evaluation-Karl Lashley (1950)
This work suggests that higher cognitive functions, such as the processes involved in learning, are not localised but distributed in a holistic way. Lashley removed areas of the cortex (10-50%) in rats that were learning a maze. No area was proven to be more important than any other in terms of their ability to learn the maze. This suggests that learning is too complex to be localised.
Lateralisation
Evaluation- Plasticity
The notion of cortical remapping (plasticity). When the brain has become damaged and a particular function has been compromised or lost, the rest of the brain is able to reorganise itself in an attempt to recover the lost function.
Lashley described this as the ‘law of equipotentiality’ whereby surviving brain circuits ‘chip in’ so the same neurological action can be achieved.
This does not happen EVERY time.
3 types of neurons:
Motor, relay and sensory
Axon:
Carries impulses away from the cell body down the length of the neuron. Covered in a fatty layer (myelin sheath) that protects the axon and speeds up electrical transmission of the impulse.
Cell body:
includes a nucleus, which contains the genetic material of the cell. Dendrites protrude from the cell body, these carry nerve impulses from neighbouring neurons towards the cell body.
Electrical transmission:
A neuron in a resting state inside of the cell is negatively charged compared to the outside. When a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second causing an action potential to occur.
Synaptic transmission-
The process by which neighbouring neurons communicate with each other by sending chemical messages across the gap that separates them.
Neurotransmitter-
Brain chemicals released from synaptic vesicles that relay signals across the synapse from one neuron to another. Neurotransmitters can be broadly divided into those that perform an excitatory function and those that perform an inhibitory function.
Excitation-
When a neurotransmitter, such as adrenaline, increases the positive charge of the postsynaptic neuron. This increases the likelihood that the neuron will fire and pass on the electrical impulse.
Inhibtion-
When a neurotransmitter, such as serotonin, makes the charge of the postsynaptic neuron more negative. This decreases the likelihood that the neuron will fire and pass on the electrical pass.
Chemical transmission- synapses.
Neurons communicate with each other in groups known as neural networks. The synapse, space between neurons, includes the presynaptic terminal and postsynaptic receptor site. Signals within neurons are transmitted electrically, but between neurons they are transmitted chemically by synaptic transmission.
Electrical impulse reaches the end of the neuron (presynaptic terminal) it triggers the release if neurotransmitter from the synaptic vesicles.
Neurotransmitter- sending signals.
Once it crosses the gap it is taken up by the postsynaptic receptor sites, here the chemical message is converted back into an electrical impulse, the process of transmission begins in this other neuron.
Summation-
Whether a postsynaptic neuron does fire is decided by the process of summation. The excitatory and inhibitory influences are summed: if the net effect on the postsynaptic neuron is inhibitory then the post synaptic neuron is less likely to fire; if the net is excitatory then it is more likely to fire- and momentarily the inside of the postsynaptic neuron becomes positively charged.
Therefore action potential of the postsynaptic neuron is only triggered if the sum of the excitatory and inhibitory signals at any one time reaches the threshold.
Localisation vs holistic theory.
Holistic- Broca, Wernicke all support the holistic theory that all parts of the brain were involved in the processing of thought and action.
Localisation is the idea that different parts of the brain perform different tasks and are involved in different areas of the body.
Plasticity:
This describes the brain’s tendency to change and adapt as a result of experience and new learning.
Functional recovery:
A form of plasticity. Following damage through trauma, the brain’s ability to redistribute or transfer functions usually performed by a damaged area to other, undamaged area.
Brain plasticity through childhood.
During infancy, the brain experiences a rapid growth in the number of synaptic connections it has, peaking at approximately 15,000 at age 2-3 years. This is twice as many than there are in adult brains.
Originally though changes were restricted to only the developing childhood brain, and that the adult brain would remain fixed in function and structure. Recent research suggests that at any time neural connections can change and form as a result of learning and experience.
