Biological Bases Of Behaviour

Central Nervous System

Consists of the brain and the spinal cord The spinal cord connects the brain to the

peripheral nervous system

Cerebral Cortex

Is the thin, folded covering of the cerebrum. The cerebrum is the largest part of the brain and consists of two halves called the cerebral hemispheres

Corpus callosum

The structure consisting of about 200 million nerve fibres that provide communication between the left and right hemispheres of the brain

Frontal Lobe

Consists of the primary motor cortex which is responsible for generating movement of body parts. Specific points are responsible for certain parts of the body (motor homunculus)

The association area is involved in expressing emotional behaviour, personality and temperament

Broca’s area (only in left hemisphere!) is responsible for the production of clear, articulate speech, as well as with analysing the grammatical structure of sentences

Parietal Lobe

Contains the somatosensory cortex, which is responsible for registering sense of touch, and receives sensory information from sensory receptors about touch, pain, pressure, muscle movement and position.

Also responsible for integrating visual information

Occipital Lobe

Regions where visual information is received and processed.

Visual association areas bring together both visual information and information from other areas of the cerebral cortex.

Enables us to form visual images of memories and to think visually

Temporal Lobe

Responsible for receiving and processing sound.

Play an important part in our ability to remember faces, and the storing of memories such as events we have experienced.

Wernicke’s area (only in left lobe!) is responsible for interpreting sound and understanding speech. Also for locating appropriate words when we speak or write

Hemispheric Specialisation

The specialisation and dominance of certain brain functions by each of the cerebral hemispheres

Whilst certain hemispheres dominate, the functions can still be taken over by the other hemisphere if damage occurs (plasticity of brain)

Functions of Left Hemisphere

Verbal functions such as reading, writing, speaking and understanding speech

Analytical functions such as mathematical logic, analysing, organising and interpreting data

Functions of the right hemisphere

Non-verbal functions such as: Recognising faces or music Spatial tasks Jigsaw puzzles Producing/ appreciating art daydreaming

Studies of people with damaged brains

Studies of brain damage by Paul Broca and Karl Wernicke showed that separate areas were responsible for language production and language comprehension

Roger Sperry’s split brain surgery showed that the left and right hemispheres were dominant in different tasks (know the results of his study!)

Studies of people with intact brains

EEG- electroencephalograph EMG- electromyograph EOG- electro-oculargram MRI- Magnetic Resonance Imaging CAT- Computerised Axial Tomography PET- Positron Emission Tomography

Spinal Cord

Column of nerve fibres that run from the base of the brain to the lower back region

31 pairs of nerves White matter- solely bundles of axons which

are covered in myelin (myelin sheath) Grey matter- contains cell bodies along with

their axons and dendrites and are located mainly near the centre of the spinal cord.

How is sensory info transmitted from the body to the brain?

Sensory information is sent from the sensory receptor cells in the PNS via sensory neurons to the CNS

How is motor information sent from the brain?

Motor information leaves the brain via motor neurons that depart the motor cortex

Message is transmitted via motor neurons down the spinal cord to the skeletal muscles in the body, the visceral muscles of the internal organs or glands which secrete hormones

At their destination they connect to effector cells which control movement or hormone secretion

The Peripheral Nervous System

Is comprised of all neurons outside of the Central Nervous System

It provides the pathway from the brain and spinal cord to all other parts of the body.

Is separated into the somatic and autonomic nervous systems

Somatic Nervous System

Has a sensory and motor function. Sensory function is to transmit info to the brain from the sensory receptors and the motor function involves moving muscles attached to the body’s skeleton.

Involves controlling skeletal muscles that are involved in movement

If the spinal cord is severed, the somatic nervous system below the point of damage becomes paralysed because the messages cannot bridge across.

Autonomic Nervous System

The network of neurons connecting the CNS to our internal muscles and organs. Controls non-skeletal muscles such as the heart, kidneys, glands, etc.

The majority of functions occur without our control, but we can gain control of some functions through biofeedback. This is a process whereby an individual receives feedback about a particular function and learns techniques to control these functions, such as meditation, relaxation, etc.

Has 2 sub-branches: Sympathetic and parasympathetic nervous systems

Sympathetic Nervous System

The branch of the ANS that provides the body with a sudden burst of energy due to needing to deal with a threatening or stressful situation.

Number of changes occur such as pupils dilate, secretion of adrenalin, increased heart rate, digestion decreases, etc.

Parasympathetic Nervous System

Returns the body to a state of homeostasis once threat or stressor has passed

Keeps the body in homeostasis (regulates internal systems and minimises energy)

Physiological Systems Involved In Arousal

Arousal- an organisms state of alertness and readiness for action

Fight-flight response- an automatic reaction by the sympathetic N.S to prepare the body for dealing with a physically or psychologically threatening situation.

Polygraph

A device that detects fluctuations in certain physiological functions that are controlled by the autonomic nervous system

Typically measures heart rate, respiration rate, blood pressure and galvanic skin response

Person is asked control questions and relevant questions, which are compared to assess arousal in the participant

Limitations include similarity in arousal levels between different emotions including lying, naturally low rates in certain people, and the participant creating high fluctuations on control questions. Produces too many false hits

Effects of Prolonged or intense arousal

Stress- a condition involving psychological and physiological tension that arises from internal or external sources

Stressor- events or circumstances that cause stress.

Stress may be acute or high in intensity, or may be chronic.

Physiological effects- fatigue and lowered immune system

Psychological effects- 3 categories; behavioural effects (shaky hands, jumpiness, furrowed brow), emotional effects (feelings of anger, depression, helplessness, irritability) and cognitive effects (forgetfulness, inability to concentrate or make decisions)

General Adaptation Syndrome (Hans Seyle)

A pattern of physiological responses an organism experiences when placed under intense or prolonged stress

Consists of 3 identifiable stages

Alarm reaction- first aware of stressor. Temporary state of shock as if injured, but quickly recovers as the sympathetic N.S is activated (countershock). Flight-fight is activated.

Resistance- resistance to stressor rises above normal level. Cortisol is released to help repair tissue, but presence lowers immune system

Exhaustion- extreme fatigue, high anxiety and depression. Illness due to low immune system.

Relationship between stress and disease

A psychosomatic illness is one in which the physical symptoms are caused or heightened by psychological factors. It is not imagined.

Conditions identified include arthritis, asthma, chronic back pain, colds, diabetes, headaches, migraines, menstrual discomfort, stomach ulcers, ulcerative colitis, cancer, heart disease and multiple sclerosis.