Chapter 14 Flashcards
Coordination and Response (23 cards)
Describe the role and parts of the nervous system
Central NS – brain and the spinal cord
Peripheral NS – rest of the nerves
role: coordination and regulation of body functions
What are neurones
nerve cells – receive and transmit signals (conduct electrical impulses) to different parts of the body
– Sensory neurones transmit nerve impulses from sense organs to the central nervous system.
– Motor (effector) neurones transmit nerve impulses from the central nervous system to effectors (muscles or glands).
– Relay (connector) neurones (also called multipolar neurones) are found inside the CNS → make connections with other neurones.
Structure of each neurone
!! refer to diagram 14.1 !!
myelin sheath insulates the neurone to make transmission of the impulse more efficient
cell body: contains cytoplasm and nucleus
motor – at the start of inside the grey matter of spinal cord
sensory – Near the end in a ganglion (swelling) just outside
the spinal cord
relay: In the centre of the neurone inside the spinal cord
dendrite: branched extensions that receive or transmit
motor – attached to the cell body
sensory – at the end of the neurone
relay – at both ends of the neurone (all around)
axon: part that takes impulses away from cell body
motor – very long
sensory – very short
relay – none
dendron: part that takes impulses toward cell body
motor – none
sensory – very long
relay – none
Describe and explain the structure of synapses
a junction between two neurones:
an impulse in the first neurone stimulates the release of
neurotransmitter molecules from vesicles which diffuse
across the synaptic cleft and bind with receptor proteins on the 2ⁿᵈ neurone to trigger an impulse since neurotransmitter substances are synthesised on only one side of the synapse, while receptor molecules are present only on the other side insures that impulses travel in one direction only
Describe what is meant by a reflex action
A means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands)
Describe a simple reflex arc
describes the pathway of an electrical impulse in response to a stimulus:
stimulus triggers a receptor which stimulates an impulse through a sensory neurone to a coordinator (spinal cord/ relay neurone) which transmits an impulse to an effector neurone conducting an impulse to an organ → response
Describe sense organs
groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals
Diagram of eye
!! refer to diagram 14.6 !!
Cornea: transparent layer at the front of the eye that refracts the light entering the eye to help focus it
Iris: coloured ring of circular and radial muscle that controls how much light enters the pupil
Lens: transparent, convex, flexible, jelly-like structure that focuses light onto the retina
Retina: light-sensitive layer containing light receptors cells
Optic nerve: carries electrical impulses from the retina to the brain
Fovea: point on the retina where the light is usually focused
Describe the light receptor cells on the retina
rods: sensitive to low light intensity; detect shades of grey
– distributed throughout the retina, but none in the centre of the fovea or blind spot
cones: sensitive only to high light intensity; detect color
– concentrated in the fovea
– three types: each sensitive to red light, green light and blue light
Explain pupil reflex
changes the size of the pupil to control the amount of light
entering the eye – too much can damage retina
→ antagonistic muscles: when one contracts the other relaxes
bright light: circular muscle contracts radial muscle relaxes - constrict pupil
dim light: radial muscle contracts circular muscle relaxes - dilate pupil
Explain accommodation
near object: rays need to be refracted more lens needs to be more convex
→ ciliary muscles contract – a smaller diameter – removes the tension on the suspensory ligaments – no pull on the lens – thicker (more convex)
distant object: rays need to be refracted less lens needs to be less convex
→ ciliary muscles relax – a larger diameter – pulls on the suspensory ligaments – pulling on the lens – thinner (less convex)
Describe hormones
chemical substance, produced by a (endocrine) gland and carried by the blood, which alters the activity of one or more specific target organs
Identify the different hormones and the glands that secrete them
adrenal glands secrete adrenaline
pancreas secrete insulin and glucagon
testes secrete testosterone
ovaries secrete oestrogen
Describe adrenaline and its effects
hormone secreted in ‘fight or flight’ situations - prepare muscles for action
– ↑se breathing rate – more oxygen for respiration for energy
– ↑se the blood glucose concentration – stimulates liver to convert glycogen to glucose for respiration for energy
– ↑se heart rate : muscles are supplied with blood containing glucose and oxygen more quickly
– ↑se pupil diameter: more light to enter eye clearly (see possible threats)
– reduces the blood supply to the skin and digestive organs, so most blood is diverted to vital organs
Compare nervous and hormonal control
type of transmission: NS-electrical ES-chemical
transmission pathway: NS-nerves ES-blood vessels
transmission speed: NS-fast ES-slow
duration of effect: NS-short ES-long
Describe and explain homeostasis
maintenance of a constant internal environment:
Negative feedback is a control mechanism in biological systems where a change in a condition triggers a response that counteracts or reverses that change. When a change from a set point is detected, a response is triggered that opposes the change to brink it back to the set point
Describe the control of blood glucose concentration
If bgc rises: the pancreas secretes insulin which stimulates the liver to convert and store the glucose as glycogen
if bgc drops: the pancreas secretes glucagon which stimulates the liver to convert glycogen back to glucose and release it into the bloodstream
Explain Type 1 diabetes and outline its treatment
failure of cells of the pancreas to produce enough insulin:
– bgc rises too much that it gets excreted in urine or falls too low that brain cells cannot work properly – coma
symptoms: feeling tired, thirsty frequent urination, weight loss – body starts to break down muscle and fat
treatment: regulated diet, exercise, regular insulin injections, regular blood tests
skin structure
!! see diagram 14.11 !!
just in case:
when cold: erector muscles contract, making hair stand up traps an insulating layer of air close to the skin, reducing heat loss (like a fur coat)
when hot: erector muscles relax, making hairs lie flat against the skin – reduces insulation more heat loss
Describe the maintenance of a constant internal body temperature in mammals
region called hypothalamus - thermoregulatory centre - receptors detect temperature changes in the blood + coordinate a response to them
when too high:
– sweating: as water evaporates, it removes heat from the skin
– vasoconstriction: arterioles wall muscles relax - wider lumen - more blood flow near surface - more heat loss via radiation
when too low:
– vasodilation: arterioles wall muscles contract - narrow lumen - less blood can pass near surface - less heat is radiated
– shivering: uncontrollable bursts of rapid muscular contraction in the limbs release heat as a result of respiration
– skin has a layer of fatty tissue - insulating properties – reduces heat loss from the skin surface
Describe gravitropism and phototropism
gravitropism: a response in which parts of a plant grow towards or away from gravity
phototropism: a response in which parts of a plant grow towards or away from the direction of the light source
Investigate and describe gravitropism and phototropism in shoots and roots
Phototropism:
select two potted seedlings of similar size and water them both. one is placed in a light-proof box with a window cut in one side, to provide one-sided light (plant A). the other is treated the same way, but set up on a turntable called a clinostat, which slowly turns so that all sides of the shoot receive light (control plant B). the shoot of plant A grows towards the light source, but the shoot of plant B grows vertically. the results suggest that shoot A has responded to one-sided light by growing towards it – positive phototropism
Gravitropism:
select a number of seedlings with straight radicles (young roots) and set them up as shown in Figure 14.13 the radicles in the clinostat (the control) continue to grow horizontally, but those in the fixed jar grow vertically downwards → that the stationary radicles have responded to gravity by growing towards it – positive gravitropism
Explain tropic responses
Auxins – plant growth substances made by the shoot & root tips of actively growing plants; an accumulation of auxin in a shoot stimulates cell growth by the absorption of water – opposite effect in roots – when they build up, they slow down cell growth
Light: auxins diffuse towards the shaded side of the shoot
→ cells stimulated to absorb more water than those on the light side – unequal growth causes the stem to bend towards the light (positive phototropism)
Gravity: auxins accumulate on the lower side of the shoot, owing to gravity → cells stimulated to absorb less water than those on the upper side – unequal growth causes the shoot bends upwards (positive gravitropism)
