Coordination and response.

electrical impulses travel along

neurones

mammalian nervous system parts

the central nervous system (CNS) consisting of the brain and the spinal cord

the peripheral nervous system (PNS) consisting of the nerves outside of the brain and spinal cord

NS function

coordination and regulation of body functions

3 types of neurones

sensory neurons - carry electrical impulses from sense organs to the CNS

relay neurons - connect both sensory and motor neurones

motor neurons - carry electrical impulses from the CNS to either muscles or glands (effectors)

neuron adapation

Lots of mitochondria to release energy, for, transmission of impulse.

Long axons to transmit impulse over long distances

Many branches to connect to other neurons

Dendrites have large surface area for many receptors

reflex arc eg

• The stimulus detected by the receptors and converted into an electrical impulse.

• The EI travels along the sensory neuron. The SN sends the electrical impulse to the CNS (coordinator)

• The electrical impulse is passed on to relay neurone in the spinal cord.

• Relay neurone connects to motor neurone and passes the impulse on.

• the motor neuron carries an electrical impulse to an effector

• the effector carries out a response

reflex arc

a means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands)

synapse

junction between two neurons

vesicles - contain neurotransmitter molecules

synaptic gap

receptor proteins

events at the synapse

* an impulse stimulates the release of a neurotransmitter molecules from vesicles into the synaptic gap
* the neurotransmitter mol diffuse across the gap
* neurotransmitter molecules bind with receptor proteins on the next neuron
* an impulse is then stimulated in the next neuron

role of synapse

ensure that impulses travel in one direction only

sense organ

groups of receptor cells responding to specific stimuli

what specific stimuli do sense organs respond to?

light,

sound,

touch,

temperature

chemicals

eye structure

function of eye parts

cornea - refracts light

iris - controls how much light enters the pupil

lens - focuses light on the retina

retina - contains light receptors, some sensitive to light of different colours

optic nerve - carries impulses to the brain

pupil reflex

involuntary response of the eye to changes to light intensity

in bright light:

pupil diameter narrows

to allow less light in

to protect the retina from damage

\----------

in dark light:

pupil diameter dilates

to allow more light in

to improve vision and see better in the dark

antagonistic pupil reflex

bright light:

• circular muscle of iris contract

• radial muscle of iris relax

• the pupil narrows/constricts

• allowing less light in

  -----------------------------

  darkness:

• radial muscles contract

• circular muscles relax

• the pupil dilates

• allowing more light in

accomodation definition/

is the function of the eye that helps it view near and distant objects

accommodation

function of the eye that helps it view near or distant objects

near objs:

ciliary muscles contract

suspensory ligaments slacken and become less tait

lens becomes thicker

the lens refracts light rays more strongly to focus on the near obj

-------------

far objs:

ciliary muscles relax

suspensory ligaments are pulled tight and become taut

this pulls the lens and makes it thinner

the lens refracts light rays less strongly

2 types of receptor cells in the retina

rods - Provide night vision. Sensitive in dim light. provide black and white vision

cones - used for colour vision is bright light. three types of cones: which are sensitive to the colours light: red, green, and blue

---------

distribution:

rods: found all over the retina except blind spot and fovea

cones: concentrated at the fovea

fovea

helps us see fine details and colours clearly

has a high concentration of cone cells that are packed tightly together to give us sharp vision

why cant we see colours in the dark

cones are less sensitive in low/dim light

cones detect colour

rods sensitive in dim light, but cannot detect colour

voluntary vs involuntary action

voluntary:

slower. takes more time.

uses high centers of the brain

learnt

not automatic.

hormones

chemical substance produced by a gland and carried by the blood, which alters the activity of one or more specific target organs

endocrine glands

(a) adrenal glands and adrenaline (b) pancreas and insulin (c) testes and testosterone (d) ovaries and oestrogen

adrenaline

defined as the hormone secreted in ‘fight or flight’ situations

it:

• increased heart rate - blood is pumped more quickly and efficiently. so more glucose and oxygen is delivered to vital muscle and organs. an increased heart rate allows carbon dioxide to be removed quickly from muscle cells

• increased breathing rate - so more glucose and oxygen to the muscles and other vital organs. an increased rate of breathing allows carbon dioxide to be removed quickly from muscle cells.

• increased pupil diameter - dilates pupil. allows more light into the eye. increase mental awareness.

metabolic effects of adrenalin

increasing the blood glucose concentration - stimulates , breakdown / conversion, of glycogen to glucose in liver. increase glucose concentration in the blood.

increasing heart rate - to provide more glucose and oxygen to the muscles for respiration

what happens if the blood glucose level is too low

• pancreas detects and releases the hormones glucagon

• in the liver glycogen is broken down into glucose

• and releases into the bloodstream

what happens if the blood glucose level too high

• pancreas detects this and releases insulin

• this stimulates liver cells to take in more glucose

• and convert glucose into glycogen for storage

comparison of nerves and hormones

• speed of transmission

• nerves - fast

• hormones - slow

• duration of effect:

• nerves - short-term

• hormones - longer lasting

• ---

  hormonal coordination is only chemical, whilst nervous communication uses both chemicals and electrical impulses.

• each hormone may have more than one target organ, whilst in nervous communication there is only one or specific target

homeostasis

the maintenance of a constant internal environment

negative feedback

• (insert condition) is kept within narrow limits

• change in body (eg skin temp)

• acts as stimulus

• to keep (insert condition at a set point) (eg keep temp at 37c)

• corrective action done by the body

type 1 diabetes and the treatment

An autoimmune condition where the body fails to control blood glucose concentration. Due to insufficient insulin production by the pancreas. The immune system cells destroy beta cells in the pancreas, which produce insulin. As a result blood glucose concentrations are too high.

treatment:

• injecting insulin

• monitor their blood glucose level regularly

• take extra care of their diet, avoiding foods high in sugar

• exercise regularly, which can lower blood glucose levels through increased muscle respiration

skin diagram

skin diagram 2

N is artery.

P is arteriole.

J is capillary.

L is shunt vessel, which redirects blood under the surface of the skin.

K is a venule.

M is vein.

temperature control when too cold

too cold:

• fatty tissue in the skin act as an insulating layer that helps prevent excess heat loss from the body through the skin

• when it is cold, the hair erector muscles contract causing the hairs to stand upright/erect. this is to trap a layer of air. air is a good insulator so it helps reduce heat loss.

• the body shivers, the muscle contractions of shivering generate heat energy through respiration. this warms the body

• muscle in arteriole wall contract. vasoconstriction occurs. less blood flows to skin capillaries. this helps reduce heat loss through the skin by radiation. Shunt vessels dilate/open. Blood is redirected away from the skin capillaries to minimize heat loss.

• this is detected by thermoreceptors in the brain and skin.

temperature control when too hot

• hair erector muscles relax, causing hairs to lie flat

• allowing air circulation

• which increases heat loss to the environment by radiation.

• sweat glands secrete sweat. sweat evaporates off the skin, and the heat is lost to the surroundings. cooling the body.

• vasodilation: muscles arteriole wall relax. vasodilation occurs. more blood flows to skin capillaries to increase the heat loss through the surface of the skin through radiation. shunt vessels constrict or close. Blood is redirected toward the skin capillaries

• this is detected by thermoreceptors in the brain and skin.

gravi 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

role of auxin in controlling shoot growth

• auxins are made in the shoot tip

• auxins diffuse down the stem

• auxins collect in the side in the dark

• the auxins stimulates greater cell elongation on side in the dark

• on this side, cells are stimulated to absorb more water, so that side of the plant grows more

• this causes the plant to grow towards the light

  ---

  Auxins accumulate on the lower side of the shoot, due to gravity.

• Cells on the lower side grow more quickly

• The shoot bends upwards.

• This is called negative geotropism. 

  (If a shoot is placed horizontally in the absence of light:)

  ---

  If a root is placed horizontally in the absence of light:
  

  • Auxins accumulate on the lower side of the root, due to gravity.

  • Auxin inhibits cell elongation.

  • Cells on the lower side grow more slowly  

  • The root bends downwards.

  • This is called positive geotropism.  

benefits of phototropism and gravitropism

more photosynthesis

more (light) energy, absorbed

more growth

(reach air for) carbon dioxide for photosynthesis ; (reach air for) oxygen for respiration ; idea that they grow tall so that flowers are exposed for, (wind / insect) pollination

roots grow downwards / towards (direction of) gravity ; to reach, water / ions or minerals ; to anchor plant in the soil ;