HPA Axis definition
Sequence of bodily activity in response to stress that involves hypothalamus, pituitary and adrenal cortex
Evaluation fight or flight response
Tend and befriend, Taylor et al, mothers protecting themselves and their young through nurturing and forming protective alliances with other women, women dif system coping w stress as primary caregivers, can't flee as easily, rat studies suggest may be a physiological response to stress that inhibits flight, hormone oxytocin, increases relaxation reduces fear decreases stress
Negative consequences, physiological responses may be adaptive for stress response, requires energetic behavioural responses. Prob arises when stress is repeatedly activated, increased blood pressure characteristic of SNS can lead to physical damage in blood vessels and eventually to heart disease, too much cortiosol surpresses immune response shutting down process that fights infection
Freeze response, prior to fight or flight, most animals inc humans freeze, 'stop, look and listen' animal hyper vigilant and alert to danger, freezing focuses attention and makes them look for new info in order to make best response for that particular threat
Further evaluation for fight or flight
Positive, Von Dawans et al challenge classic sex differences under stress, acute stress greater co-operation and friendly behaviour, human connection after a disaster e.g 9/11, humans are fundamentally social and our protective nature has allowed us to thrive
Genetic basis to sex differences in fight or flight response, Lee and Harley evidence of a genetic bass for gender differences, SRY gene on male Y chromosome directs male dev promoting aggression resulting in fight or flight due to stress. SRY may prime males to respond in this way by releasing stress hormones e.g adrenaline, increased blood flow to organs. Absence of SRY in humans with oestrogen and oxytocin action may prevent fight or flight
Autonomic nervous system definition
Governs brains involuntary activities, e.g stress, heartbeat and is self regulating, divided into sympathetic branch (fight or flight) or parasympathetic branch (rest and digest)
Brain definition
Part of the NS that is responsible for co-ordinating sensation, intellectual and nervous activity
CNS definition
Brain and spinal cord, receives info from senses, controls body's response
Peripheral NS definition
Part of the NS outside of brain and spinal cord
Somatic NS definition
Part of peripheral NS responsible for carrying sensory and motor information to and from CNS
Spinal cord definition
Bundle of nerve fibres enclosed within spinal column and connects nearly all parts of the body with the brain
How does the CNS work
Controls behaviour and regulates physiological processes, brain must receive info from sensory receptors eg eyes, and send messages to the muscles and glands, involves spinal cord and the brain
Spinal cord and CNS
Relay info between brain and rest of the body, monitor and regulate bodily processes e.g. breathing and coordinate voluntary movements. Connected by pairs of spinal nerves branched off from thoracic region, carry messages to chest and part of the abdomen, contains circuit of nerve cells that allow simple reflexes without brain. If damaged, areas below spinal nerves cut off from the brain, stop functioning
Brain and CNS
Cerebum, four different lobes, each dif function. Frontal thought and production of speech, occipital processing of visual images. Split two halves, cerebral hemispheres, dif jobs, communicate through corpus callosum. Cerebellum at back, motor skills and balance, coordinating muscles to allow precise movements, abnormalities speech and motor problems. Diencephalon beneath cerebrum top of brain stem, thalamus and hypothalamus. Thalamus relay station for nerve impulses from senses, routing them to correct part to be processed. Hypothalamus, body temp, thirst, links endocrine system and NS, controlling release of hormones from pituitary. Brain stem, regulating automatic functions essential for life, e.g. heartbeat, motor and sensory neurons travel through, allow impulses pass brain and SC.
Somatic NS
12 pairs of cranial nerves (emerge from underside of the brain) and 31 pairs of spinal nerves (from spinal cord), both sensory and motor neurons, sensory relay messages to CNS, motor relay info from CNS to other areas, involved in reflex actions without CNS boosts speed
Sympathetic NS
Responses that help us deal with emergencies e.g fight or flight, increase heart rate blood pressure dilating blood vessels in the muscles, neurons from the SNS go to every organ and gland, prep body for rapid action when threatened, e.g release stored energy pupils dilate hair stands on end, slows processes digestion and urination
Parasympathetic NS
Relaxes them after emergency passed, SNS causes heart to beat faster and blood pressure increase, slows heartbeat and reduces blood pressure, digestion begins again, involved with energy conservation and digestion, rest and digest
Types of neurons definitions
Motor, synapses with muscles, control contractions
Relay, most common in CNS, allow sensory and motor communication
Sensory, carry nerve impulses from sensory receptors to spinal cord and brain
Neurons
Specialised cells that carry neural info through body. Dendrites at one end receive signals from other neurons or sensory receptors. Connected to cell body, control centre. Impulse carried along axon, terminates at axon terminal. Insulating layer around axon, myelin sheath, allows nerve impulses to transmit more rapidly along axon, if MS damaged impulses slow down, length of neuron few mm's to one metre
Sensory neurons
Carry nerve impulses to sensory receptors (e.g for vision, taste) to spinal cord and brain, eyes ears tongue skin, convert info from these receptors into neural impulses, when reach brain translated into sensations e.g heat so appropriate reaction, not all sensory info travels as far as the brain, some terminate at SC, allows quick reflexes without delay of sending impulses to the brain
Relay neurons
Most neurons either sensory nor motor, lie somewhere between sensory input and motor output, allow communication, lie wholly within brain and SC
Motor neurons
Neurons located in the CNS that project axons outside CNS and directly/indirectly control muscles, form synapses w muscles and control contractions, when stimulated releases NT's bind to receptors on muscle, trigger response which leads to muscle movement, axon fires muscle contracts, strength of muscle contraction depends on axon firing rate that control it, muscle relaxation caused by inhibition of motor neuron
Synaptic transmission definition
Process by which a nerve impulses passed across the synaptic cleft from one neuron (presynaptic neuron) to another (postsynaptic neuron)
Process of synaptic transmission
Action potential reaches synaptic vesicles, causes them to release their contents through exocytosis, contain NT's. Released NT diffuses across gap between pre and post-synaptic cell, binds to special receptors on cell surface that recognise it and are activated by that NT. Once activated, either excitatory or inhibitory effect.
Reuptake during synaptic transmission
Fraction of a second, effects terminated at most synapses. NT taken up again by presynaptic neuron, stored for later. How quickly presynaptic takes back NT determines how prolonged its effects will be, quicker shorter effects on post synaptic neuron, some AD's inhibit reuptake leaving NT at synapse for longer
Excitatory and inhibitory NT's
Excitatory, noradrenaline acetylcholine, on switches, increases likelihood that signal is sent to postsynaptic cell, more likely to fire.
Inhibitory, serotonin GABA, off switches,decrease likelihood neuron will fire, calm mind and body inducing sleep filter out unnecessary excitatory signals.
Post synaptic potential
Inhibitory bind w receptor results in IPSP, less likely cell will fire. Excitatory bind w receptor causes electrical change in cell membrane, EPSP, cell more likely to fire.
Likelihood of cell firing, adding up excitatory or inhibitory input, net result summation determines whether or not cell fires. Increase strength of EPSP, spatial large number of EPSP's gen at many dif synapses at same time, temporal large numbers of EPSP at same synapse by series of high frequency action potentials. Rate fired, what goes on in synapses, if excitatory synapses more active cell fires at high rate, if inhibitory cell fires lower rate or not at all
Endocrine system definition, glands, hormones
ES, network of glands throughout body, manufacture and secrete chemical messengers known as hormones
Endocrine glands, special groups of cells within ES, whose function is to produce and secrete hormones
Hormones, body's chemical messengers, travel through bloodstream, influence many dif processes inc mood stress response mother baby bonding
Endocrine glands
Produce and secrete hormones, chemical substances that regulate activity of cells or organs in the body, pituitary adrenal and reproductive organs (ovaries and testes), each gland produces dif hormones which regulate organ activity and tissues activity, regulated by feedback similar to a thermostat, signal from hypothalamus to pituitary gland as a 'releasing hormone', causes pituitary to secrete stimulating hormone into bloodstream, signals to target gland to secrete its hormone, rising levels in bloodstream, hypothalamus shuts down releasing pituitary shuts down stimulating, slows down secretion of target gland hormone, stable concentrations of hormones in bloodstream
Hormones
Target cells respond to a particular hormones if they have receptors for it, cells that don't cant be influenced directly by that hormone, when enough receptor sites stimulated by hormones results in a physiological reaction in the target cell, timing critical for normal functioning as are the levels released, too much or too little equals bodily system dysfunction, e.g too much cortisol Cushing's syndrome high blood pressure and depression, most common cause excess cortisol tumour in pituitary gland, makes too much adrenacorticotrophic hormone, stimulates adrenal glands to make too much cortisol
Pituitary gland
Master gland, primary function to influence the release of hormones from other glands, regulate many body functions, controlled by hypothalamus, receives info from many sources about basic functions of the body uses info to regulate these. Master gland, produces hormones that travel in bloodstream to their specific target, either directly cause changes in physiological processes in body or stimulate other glands to produce other hormones, high levels of hormones produced in other endocringe glands, stop hypothalamus and pituitary releasing more of their own hormones, negative feedback, prevents hormones rising too high
Hormones produced by pituitary gland
Anterior (front), posterior (back). Anterior releases ACTH due to stress, also produces luteinising hormone and follicle stimulating hormone used in reproduction. In females, these stimulate ovaries to produce oestrogen and progesterone, males stimulate testes to produce testosterone and sperm. Posterior, releases oxytocin, stimulates contraction of uterus during childbirth important for mother-infant bonding.
Adrenal glands
On top of kidneys, two parts. Outer part adrenal cortex, inner region known as adrenal medulla, hormones released by the adrenal cortex are necessary for life, those released by adrenal medulla are not
Hormones produced by the adrenal glands
Adrenal cortex produces cortisol, regulates or supports number of important bodily functions inc cardiovascular. Cortisol increased due to stress. If too low, low blood pressure, poor immune function and inability to deal with stress. AC, Aldosterone, responsible for maintaining blood volume and blood pressure. Adrenal medulla, releases adrenaline and noradrenaline, prepare body to fight or flight. Adrenaline helps with stress, increases heart rate and blood flow to muscles and brain, help convert glycogen to glucose to provide energy. Noradrenaline constricts blood vessels causing blood pressure to increase
Ovaries and testes
Ovaries, part of female reproduction system, responsible for egg production, oestrogen and progesterone. Progesterone, key in post ovulation phase of menstrual cycle, associated with heightened sensitivity to social cues indicate presence of social opportunity e.g recruiting allies or threat e.g from outsiders that are significant in the case of pregnancy.
Testes, produce testosterone, causes dev of male characteristics such as growth of facial hair during puberty, testosterone controlled by hypothalamus and pituitary gland. Hypothalamus instructs PG how much to produce, PG passes it onto testes. Hormone role in sex drive, muscle strength etc, women have a very small amount of it
Fight or flight response definition
Sequence of activity, triggered when body prepares itself to defend or attack (fight) or run away to safety (flight), involves changes in NS, secretion of hormones necessary to sustain arousal
Fight and flight response to stress, amygdala and hypothalamus
When threatened, amygdala in brain mobilised, associates sensory signals with emotions associated with fight or flight e.g anger, sends distress signal to hypothalamus. Hypothalamus control centre, communicates with body through sympathetic NS, body's response to stressors involves 2 major systems, one for acute sudden stressors e.g personal attack, one for chronic ongoing stressors such as a stressful job
Response to acute (sudden stressors), sympathetic NS
Sympathetic NS, when triggered, begins process of prepping the body for rapid action necessary for fight or flight, SNS sends a signal through to adrenal medulla, responds by releasing adrenaline into the bloodstream
Response to acute (sudden stressors), adrenaline
As it circulates, causes physiological changes. Heart beats faster, pushes blood to the muscles heart and other vital organs, blood pressure increases. Breathing more rapid to increase oxygen intake, adrenaline triggers release of blood sugars and fats, floods the bloodstream and supplies energy for fight or flight
Response to acute (sudden stressors), parasympathetic NS
When threat passed, dampens down stress response. Slows down heartbeat, reduces blood pressure, digestion begins again
HPA Axis, response to chronic ongoing stress
If threat continues, kicks, hypothalamus activates stress response.
H, hypothalamus. Relies on series of hormonal signals to keep SNS working, releases corticotrophin-releasing hormone in response to threat, released into bloodstream
P, pituitary gland, CRH causes it to produce and release adrenocorticotrophic hormone, from gland ACTH is transported in the bloodstream to its target site
A, adrenal glands, ACTH stimulates adrenal cortex to release stress-related hormones, cortisol responsible for several effects in body key to fight to flight response, some are positive e.g quick burst of energy, others negative e.g lowered immune response
Feedback, self regulating, special receptors monitor cortisol levels, if rise above normal initiate a reduction in CRH and ATCH levels