Biological Basis of Behaviour Flashcards
Structure of a neuron
Information carries of the nervous system
Dendrites - carry info from sensory organs to neuron
Axon - carry info from neuron to muscles or other neurons
Axons covered by a white myelin sheath that increase the speed at which info is carried.
Working of nerve impulses
Nerve impulses are electrical events of short duration that move along the axon.
Resting neuron is negatively charged. Stimulus makes it little less negative.
When neuron reaches threshold, channels in the cell membrane open to allow positive sodium ions to enter, making the neuron temporarily positive.
This rapid change to positivity is nerve impulse. And then the next region is excited and that’s how it moves.
Neuron returns to origin state with outward flow of potassium ions.
Neurotransmitters
A chemical substance which is released at the end of a nerve fibre by the arrival of a nerve impulse and, by diffusing across the synapse or junction, effects the transfer of the impulse to another nerve fibre, a muscle fibre, or some other structure.
Eg: Dopamine [movement & emotional response], serotonin [mood, eating & pain regulation]
Peripheral nervous system
Parts of nervous system outside skull and spine.
Carries nerve impulses from sensory recpetors to CNS & carries info from CNS to muscles and glands.
Somatic [activate striped muscles] & autonomic nervous system [activate smooth muscles]
Autonomic nervous system has sympathetic [stress arousal] & parasympathetic nervous system [rest]
Afferent vs efferent nerve fibres
Afferent nerve fibres carry information through the spinal cord from body to brain
Efferent nerve fibres carry information through the spinal cord from brain to muscles
3 divisions of the brain stem
Medulla, pons, midbrain
Function of the cerebellum
Receives sensory input from brain, spinal cord and forebrain; processes this info and sends it back out to parts of the brain to coordinate movements precisely and smoothly
Reticular formation
Core of the brain stem contains many nerve fibres and neurons called reticular formation.
Ascending fibres of this RF are responsible for arousal of the cerebral cortex and are called the ascending reticular activating system. Responsible for varying degrees of arousal - deep sleep to alert wakefulness.
Coma is when portions of the ARAS are damaged.
Thalamus
Lies in the region of the forebrain, between two cerebral hemispheres.
Contains many nuclei - Some receive information from the senses and send them to the specific areas of the cerebral cortex; relay function. Others receives inputs from within the thalamus and send to the cortex.
Hypothalamus
Lies under the thalamus.
Performs the function of maintaining homeostasis in the body. Hormones and other chemicals are monitored by specialized neurons.
Change in homeostasis activates hypothalamic neuron, that send signal to other parts of the nervous system and pituitary gland.
Triggers motivated behaviour and automatic physiological adjustment.
Hormones
Chemical messengers secreted in specific glands that are released into the blood stream and carried to various parts of the body
Function of the cerebrum
Initiation of movement, coordination of movement, temperature, touch, vision, hearing, judgment, reasoning, problem solving, emotions, and learning
Contains frontal lobe, temporal lobe, occipital lobe and parietal lobe
Frontal lobe association cortex
Aka prefrontal cortex
Personality & general behavior: Prefrontal damage often leads to irritability, aggressiveness, lack of restraint, impulsivity, apathy, immaturity, loss of initiative.
Intellectual function: Damage to PF shows lack of direction in actions, preservation, inflexibility. Subtle memory impairments. Difficulty with voluntary control of eye gaze.
PF involved in sequence and ordering of actions and thoughts.
Parietal lobe association cortex
The part of the parietal lobe that lies behind the primary sensory cortex (behind the central sulcus) takes in input from visual cortex, auditory cortex, somatosensory cortex and thalamus. Output goes to thalamus and frontal & temporal cortex to control movement.
Damage to right PAC: Contralateral neglect
Damage to left PAC: Problems in writing, arithmetic, reading. Difficulty in distinguishing left from right, and short term verbal memory.
Damage to either side of PAC: Touch agnosia, perceptual problem of not recognizing common objects.
Temporal lobe association cortex
Hippocampus & amygdala (from limbic system) in temporal cortex help in memory formation
Sensory function: Auditory agnosia, visual agnosia, impaired attention
Language function: Left temporal lobe contains wernicke’s area; damage causing impairment in understanding speech and written language
Memory: Patient HM
Broca’s versus Wernicke’s area
Wernicke’s area: Belongs to the upper temporal lobe. Controls comprehension of language. Organizes spontaneous speech.
Damage- Wernicke’s aphasia, speech is fluent and well pronounced but words don’t make any sense. Inability to repeat spoken word; difficulty naming common objects; difficulty reading and writing
Loss of ability to comprehend written & spoken language - receptive aphasia
Broca’s area: Belongs to the lower frontal lobe. Contains programs for complex patterns of muscle movement needed in speech.
Damage- Broca’s aphasia, speech is not fluent and ungrammatical. Broken speech.
Loss of ability to speak - expressive aphasia
Damage to arcuate fasciulus (bundle of nerves connecting W & B)- dyslexia
Functions of the left and right hemisphere of the brain
Left hemisphere: Controls speech, comprehension, arithmetic, and writing
Right hemisphere: Controls creativity, spatial ability, artistic, and musical skills
Divided brain experiment
Left hem: language
Right hem: analysis of patterns of sensory info
Experiment done on people whose corpus callosum is severed.
Word ‘ring’ shows on right side and key is held by left hand. So word reaches left hem and key goes to right hem.
Patient will report speech info going to left hem; but not the one going to right hem (cause left controls speech and does not receive info from right).
Right hem can identify the key if it is given a nonverbal way of identifying it.
Term for evolutionary development in humans
Phelogeny
Superior vs inferior colliculus
Present in midbrain
SC - receives visual sensory input
IC - receives auditory sensory input
Thalamus
Sensory relay station
Receives sensory impulses (except smell) and transmits them to diff parts of brain
Osmoregulation happens in the _____.
Hypothalamus
maintenance of water balance
Aphagia
Damage to the lateral hypothalamus (hunger center) leading to refusal to eat or drink until forced with tubes
Tested on rats
Hyperphagia
Damage to ventromedial hypothalamus (satiety center) leading to excessive eating
