(5) Animal Responses Flashcards
Organisation of the nervous system
Nervous system divides into central nervous system (brain and spinal cord), and peripheral nervous system (neurones connecting CNS to rest of body.
PNS divides into autonomic (constant, unconscious control) and somatic (conscious control).
ANS divides into sympathetic (increases response) and parasympathetic (decreases response). Antagonistic.
Structure of the brain
Cerebrum - voluntary actions, highly folded means large surface area for lots of neurones.
Cerebellum - controls unconscious functions like posture and balance.
Medulla oblongata - controls regulatory centres of ANS, heart rate and breathing rate.
Hypothalamus - controls homeostasis, regulates thermo and osmoregulation. Regulations secretion by pituitary gland.
Pituitary gland - controls most glands. Anterior (reproduction and growth), posterior (stores and realises hormones from the hypothalamus).
Reflex arc
Stimulus, receptor, sensory neurone, relay neurone, motor neurone, effector, response.
Knee jerk reflex - spinal. Does not go to the brain. Stretch of patella tendon acts as stimulus, initiates reflex arc, causing muscle to contract.
Blinking reflex - cranial - occurs due to stimulation of the cornea to protect it. Can detect brain function in unconscious patients.
Survival importance - involuntary - the brain can deal with more complex responses, innate - do not have to be learnt providing immediate protection, extremely fast - reflex arc is short.
Coordination of responses by the nervous and endocrine systems - fight or flight
Fight of flight response.
Hypothalamus activates the sympathetic nervous system, activates the adrenal medulla and releases neurotransmitters that can also work as stress hormones. Impulses also activate glands ans muscle. ACTH released from adrenal cortex.
Neural activity combines with hormones in the bloodstream to bring about a response.
Increases breathing rate and diameter or airways to get more o2 for respiration and make ATP for muscles. Increases blood flow to skeletal muscle. Dialate pupils. Liver releases glucose.
Adrenaline is protein bases, so cannot move through the bilayer. Adrenaline binds to the receptor (first messenger), so adenyl cyclase becomes active and converts ATP to cyclic AMP (second messenger). This activates more enzymes causing a cascade effect.
Controlling heart rate with hormonal and nervous systems
Baroreceptors detect change in blood pressure (aorta).
Blood pressure too high = impulses to the medulla (centre that decreases heart rate). Sends parasympathetic nerve to SAN, less impulses so heart rate and blood pressure decreases.
Blood pressure too low = impulses to medulla (centre that increases heart rate). Sympathetic nerve to SAN, increase impulses so heart rate and blood pressure increase.
Chemoreceptors detect chemicals (change in pH).
Blood pH increases = frequency of impulses to medulla (centre that decreases heart rate) decreases. Parasympathetic nerve, less impulses to SAN causes hr and bp to decrease.
Blood pH decreases (too much co2 in blood) = frequency to medulla (centre that increases heart rate) increases. Sympathetic nerve, more impulses to SAN, causes decrease in heart rate and pH.
Types of muscle
Skeletal - striated, multinucleate, cylindrical. Controlled by somatic nervous system. Contracts quickly and fatigues quickly. Moves the bones about the joints.
Fast twitch - contracts quick, fatigue quick, used in anaerobic respiration, can generate ATP from ADP in anaerobic conditions. Slow twitch - contracts slower, fatigues slow, used in aerobic respiration, contains myoglobin - appears darker under microscope.
Involuntary (smooth) - unstriated, single, spindle shaped. Controlled by autonomic nervous system. Contracts slow and fatigues slow. Responsible for peristalsis, pupil dilation and constriction, vasodilation/constriction.
Cardiac - striated, single, cylindrical branched cells, contain intercalated disks each with their own nucleus. Controlled by autonomic nervous system, some under myotonic control. Contracts quickly and does not fatigue. Cause heart to contract and relax.
Neuromuscular junction
Connects motor neurone to muscle fibre (motor end plate). All muscle fibres in motor unit are stimulated by single motor neurone. Brain controls strength of contraction by altering number of units stimulated - graduation of response.
Impulse arrives at NMJ, calcium ion channels open causing vesicles to fuse with membrane, releasing acetylcholine by exocytosis.
Ach bonds with receptors on sarcolemma, causing depolarisation, which travels down t systems.
Calcium released from sarcoplasmic reticulum binds to protein in muscles, causing contraction.
Acetylcholinesterase breaks down Ach so contraction only occurs when impulses arrive continuously.
Sliding filament theory
During contraction : sarcomere = shorter, H zone (myosin only) = shorter, I band (actin only) = shorter, Z lines (actin) = closer, A band (both) = no change.
Actin - globular beads, 2 actin molecules coiled around each other. Tropomyosin wraps around actin filament. Troponin forms balls along the filament.
Myosin - 2 protruding heads and long tail, heads contain ATPase.
Tropomyosin blocks myosin head from binding site on actin.
Action potential causes Calcium ions released from sarcoplasmic reticulum binds to troponin causing Tropomyosin to pull away from binding sites.
Calcium ions activate ATPase which breaks down ATP to provide energy for muscle contraction this causes the Head to change angle, moving along actin filament.
ATP provides energy to break the cross bridge so the myosin head can reattach further along the filament. This continues while calcium ions are still binding to troponin
Role of ATP sin sliding filament theory
Breaks the cross bridge.
Actively transports calcium back into sarcoplasmic reticulum when contraction stops.
Reactions with creatine to form creatine phosphate to maintain ATP supply.
Protein synthesis.
How energy supply is maintained.
Creatine phosphate - reserve supply of phosphate, available to combine with ADP ago form ATP.
Used for short bursts of vigorous exercise.
During relaxation, creatine phosphate is replenished.
