5.5 Plant & Animal Responses Flashcards
Describe the central nervous system
-Brain : relay neurones, multiple connections for complex neural pathways. Mostly non-Myelinated grey matter.
-Spinal Cord: non-myelinated central grey matter, myelinated outer white matter ( carries APs down spinal cord for rapid, long distance communication ).
Protected by vertebral column.
Describe the peripheral nervous system
- sensory and motor neurones bundled in a connective tissue sheath to form nerves
- ensures rapid communication between sensory receptors, CNS, and effectors.
Describe the motor nervous system
- conducts APs from CNS to effectors
- somatic nervous system: motor neurones that conduct APs from CNS to voluntary effectors (e.g skeletal muscles). mostly myelinated for rapid responses. one motor neurone only.
- autonomic nervous system: motor neurones that conduct APs from CNS to involuntary effectors (e.g glands cardiac muscle, smooth muscle ) mostly non-myelinated (don’t need rapid response). At least 2 motor neurones, connected at ganglia.
Describe the sensory nervous system
-sensory neurones conduct APs frim sensory receptors to the CNS. cell body in dorsal root leading into spinal cord short axon connects to CNS neurones.
Describe the sympathetic (autonomic) motor system
Sympathetic (prepares for activity) -many nerves leading out CNS, each to a separate effector. -ganglia just outside CNS -short pre-ganglionic neurones -long post-ganglionic neurones -noradrenaline neurotransmitter -increases activity -most active during stress Effects: -increases heart rate -dilates pupils -increases ventilation rate -reduces digestive activity -orgasm
Describe the parasympathetic (autonomic) motor system
Parasympathetic (conserves energy) -few nerves leading out CNS which divide to different effectors -ganglia in effector tissue -long pre-ganglionic neurones -short post-ganglionic neurones -acetylcholine neurotransmitter -decreases activity -active during sleep/ relaxation Effects: - decreases heart rate -constricts pupils -reduces ventilation rate -increases digestive activity -sexual arousal
Briefly describe the parts of the brain
- Cerebrum: largest part, organises most higher thought processes ( conscious thought & memory )
- Cerebellum: coordinates movement and balance
- Hypothalamus and Pituitary Complex: organises homeostatic responses and controls physiological processes
- Medulla Oblongata: coordinates autonomic responses
Describe the cerebrum
-2 cerebral hemispheres connected by corpus callosum (neurones)
-outer layer = cerebral cortex (nerve cells)
Controls : -conscious thought
-conscious actions
-emotional responses
-intelligence, reasoning, judgement, decision making
-factual memory
Divided into Areas:
-sensory areas receive APs indirectly from sensory receptors. size of region = sensitivity of area inputs are from
-association areas compare inputs to previous, interpret and judge a response
-motor areas send APs to effectors. size of region= complexity of movement. motor areas on left side of brain control right side of body.
Describe the cerebellum
- balance and fine coordination of movement. receives info from many sensory receptors (e.g. retina spindle fibres)
- balance, judging position of objects and limbs, tensioning muscles to use tools, coordinating contraction and relaxation of antagonistic skeletal muscles.
- nervous pathways strengthened by practise
- connected to cerebrum by pons
Describe the hypothalamus
-controls homeostatic mechanisms
-contains its own sensory receptors
-acts by negative feedback
Temperature regulation: hypothalamus detects change in body temperature & receives input from sensory receptors in skin. initiates response for change via nervous or hormonal system.
Osmoregulation: osmoreceptors monitor water potential of blood, osmoregulatory centre initiates a response to reverse the change via the hormonal system.
* if via hormonal it acts via the pituitary gland
Describe the pituitary gland
- posterior lobe linked to hypothalamus by neurosecretory cells. hormones such as ADH pass down the neurosecretory cells and are released into blood from pituitary gland
- anterior lobe produces hormones that are released in response to releasing factors produced by hypothalamus. control response to stress, growth, reproduction, lactation
Describe the medulla oblongata
-controls non-skeletal muscles ( cardiac and involuntary smooth ) by sending APs via the autonomic NS.
Contains centres to regulate:
-cardiac centre: heart rate
-vasomotor centre : circulation and BP
-respiratory centre: rate and depth of breathing
*coordinate functions by negative feedback
-receive sensory information
explain the blinking reflex
-causes temporary closure of eyelids to protect the eyes from damage
-cranial reflex (passes through the brain)
-reflex arc as receptor and effector in same place
Stimulated by changes in environment:
-foreign object touching eye (corneal reflex)
-sudden bright light (optical reflex)
-loud sounds
-sudden movements close to eye
explain the corneal reflex
** what’s special about it?
- sensory neurone from cornea enters the pons. synapse connects sensory and relay which passes the AP to the motor neurone. motor passes out brain to facial muscles. rapid (0.1s). usually causes both eyes to blink.
- sensory neurone also passes the AP to myelinated neurones in the pons. carry it to sensory region in cerebral cortex. this allows the reflex to be overridden by conscious control. the cerebral cortex can send inhibitory signals to the motor centre in the pons. the myelinated neurones transmit the AP more rapidly than the non myelinated neurones in the pons. the inhibitory AP prevents the formation of the AP in the motor neurone.
explain the optical reflex
protects light sensitive retina cells from damage. retina detects stimulus and optical centre in cerebral cortex mediates the response. slower than the corneal reflex.
explain the knee jerk reflex
- spinal reflex
- involved in coordinated movement and balance
- quadriceps contracts to straighten leg, attached to lower leg by patella tendon. when muscle at front of thigh stretched ( knee bent / leaning backwards ), stretch receptors detect. if unexpected a reflex action causes contraction of the muscle.
- rapid
- sensory -> motor
- higher parts of the brain told that its happening but cant inhibit ( no relay )
- when walking / running cerebellum inhibits the reflex via inhibitory action potentials to the reflex arc to prevent contraction of opposing muscle.
Explain the physiological changes during the fight or flight response
- pupils dilate: more light enters eyes making retina more sensitive
- Heart rate and BP increase: increases rate of blood flow to deliver more oxygen and glucose to muscles and to remove CO2 and toxins
- arterioles to skin and digestive system constricted whilst those to muscle and liver are dilated : diverts blood flow away from skin and digestive system to muscles.
- blood glucose levels increase: supplies energy for muscular contraction
- Metabolic rate increases: converts glucose to usable forms of energy such as ATP
- erector pili muscles in skin contract: hairs stand up, sign of aggression
- Ventilation rate and depth increase: increases gaseous exchange so more O2 enters blood for aerobic respiration
- Endorphins released in brain: wounds don’t prevent activity
briefly describe how the fight or flight response is coordinated
1) inputs from sensory receptors feed into sensory centres in the cerebrum
2) cerebrum passes signals to association centres
3) if a threat is recognised, the cerebrum stimulates the hypothalamus
4) hypothalamus increases activity in the sympathetic nervous system and stimulates the release of hormones from the anterior pituitary gland.
explain how the sympathetic nervous system brings about the long term fight or flight response ( adrenaline ) (D)
-sympathetic nervous system activates the adrenal medulla to secrete adrenaline into the bloodstream.
describe the mechanism of adrenaline action
- first messenger (AA derivative that cant enter cells)
- binds to adrenaline receptor on plasma membrane, receptor associated with a G protein which is stimulated to activate adenyl cyclase
- adenyl cyclase converts ATP to cAMP which is the second messenger
- cAMP causes a series of enzyme controlled reactions that bring about the response
explain the use of releasing hormones in the fight or flight response (D)
- hypothalamus secretes releasing hormones into blood. they pass down a portal vessel to the pituitary gland and stimulate the secretion of tropic hormones from the anterior pituitary.
1) Corticotropin-releasing hormone CRH from Hypo causes release of Adrenocorticotropic hormone ACTH. ACTH causes adrenal cortex to release corticosteroid hormones ( e.g. glucocorticoids- cortisol )which regulate carb metabolism to release more glucose ( from glycogen or fat/ protein )
2) Thyrotropin-releasing hormone TRH causes release of thyroid-stimulating hormone TSH which stimulates thyroid gland to release more thyroxine (hormone) which acts on many cells, increases metabolic rate and makes cells more sensitive to adrenaline.
how can heart action be modified?
- raising or lowering heart rate (bpm)
- altering force of contractions of ventricular walls
- altering stroke volume
explain the control of the heart rate by the cardiovascular centre
- at rest the SAN controls the heart rate. however the frequency of the waves can be altered by output from the cardiovascular centre in the medulla oblongata
- nerves from cardiovascular centre ( part of autonomic NS ) supply the SAN, altering frequency of contraction
- APs sent down a sympathetic (accelerans) nerve and cause the release of neurotransmitter noradrenaline at the SAN to increase heart rate.
- APs sent down parasympathetic (vagus) nerve release neurotransmitter acetylcholine which reduces the heart rate
