chapter 6 - detecting and regulating change

Question 1

what is a thermoreceptors

Answer 1

• heat / cold changes in temp (stimulus), located in skin (peripheral thermoreceptors) / sense organ (hypothalamus, mucous membranes, abdominal organs - central thermoreceptors)
• regulates: sends message to hypothalamus to regulate body temp when nerve endings are stimulated by heat / cold (peripheral thermoreceptors cannot do both)

Question 2

what are osmoreceptors

Answer 2

• osmotic pressure detected by the concentration of substances dissolved in water in the bloods plasma (stimulus), located in hypothalamus
• regulate: send message to posterior pituitary to release ADH (from hypothalamus) to regulate water (osmotic pressure)

Question 3

what are chemoreceptors

Answer 3

• particular chemicals (stimulus), located in nose (smell), mouth (taste), BV (pH levels), blood (concentration of O2 + CO2), medulla, aorta, carotid artery, pancreas / islets of langerhans
• regulate: breathing and heartbeat

Question 4

what are touch receptors

Answer 4

• light / strong touches or pressure (stimulus), located in skin (light touch receptors in epidermis / strong touch receptors in dermis), and internal organs
• regulate: helps us to be aware of anything we touch, if there is too much pressure we respond faster, helps protect us and avoid damage, can adapt to light touches

Question 5

what are pain receptors

Answer 5

• stimulates by damage to tissue / pain / cut / excessive heat or chemicals, located in skin, mucous membranes and most organs (not brain)
• warns us about damage to tissue so that we can take evasive action to seek medical help, pain continues until stimulus removed, don’t adapt

Question 6

what is a reflex

Answer 6

• rapid, automatic response to a change in the external / internal environment, involved in maintenance of homeostasis
• properties: stimulus (required to trigger a reflex, not spontaneous), involuntary action (occurs without conscious thought), rapid response (small number of neurons involved) and they are stereotyped (occurs same way every time it happens)

Question 7

what is a spinal reflex

Answer 7

• involuntary reflexes coordinated by spinal chord (only some reflexes go to the brain)
• reflex arc pathway: name given to the pathway of impulse from receptor to effector muscle, impulses are sent to brain after the response has occurred
• purpose: protect body from injury (sneezing, coughing, constriction of pupil, sperm ejaculation)

Question 8

explain the steps in the reflex arc

Answer 8

1. receptors in the skin / sensory organ detect change / stimulus and produce a nerve impulse
2. nerve impulse travels along sensory neuron from dendrites to the axon terminal in the dorsal root via the dorsal root ganglion
3. synapse occurs in the spinal chord, nerve impulse triggers a chemical message causing synaptic vessels to move towards the membrane and fuse with it, vesicles then release neurotransmitters which diffuse across the membrane through exocytosis, diffuses
   across the synaptic cleft (synapse) and binds to receptors on dendrites of postsynaptic cell (interneuron)
4. electrical impulse continues along interneuron (CNS processes impulse)
5. another synapse takes place between interneuron and motor neuron (step 3) at the same time a nerve impulse travels to the brain to allow us to understand what has happened
6. nerve impulse continues along motor neuron towards the effector muscle, where a neuromuscular junction occurs
7. effector muscle responds to message and a response / reaction takes place

Question 9

what is a receptor

Answer 9

• structures able to detect change in body’s internal / external environment

Question 10

what are the types of reflexes

Answer 10

• protective: present at birth (sneezing, coughing, blinking)
• acquired: learnt through constant repetition to avoid harm (breaking in a car, maintaining balance)