Coordination & response B13.1

BIO IGCSE

Coordination

receptors pick up stimuli → pass to effectors = coordination.

Define sensitivity stimulus, receptors and effectors

• 1 characteristic of living organisms is:

  • The ability to detect and respond to changes in their environment.

  • This is sensitivity
    

• A stimulus is:

  • a change in the environment of an organism

• Stimuli are detected by:

  • receptors which are:

    • Specialised cells

    • able to detect specific types of changes in the environment. (detect the stimuli)

• When receptors detect a stimulus

  • it triggers a RESPONSE

  • The response is carried out by effectors

  • Response could be voluntary or involuntary

EFFECTOR TYPES:

• Muscles

  • respond by contracting

  • This causes movement

• Glands

  • respond by secreting substances

  • eg. salivary glands secrete saliva when smelling good food.

FOR SURVIVAL:

• organisms NEED a fast communication between receptors and effectors…

  • Because... 

  • animals need to catch food

  •  animals need to avoid danger,

  • so they MUST respond quickly

• Therefore there must be efficient communication between receptors and effectors

  •  so effectors act at the correct time for perfect coordination e.g. touching something hot…

electric impulses

communication in the nervous system occurs using:

• electric impulses

• nerve impulses = electric impulses that pass through nerve cells (neurones)

• nerve cells are called neurones

these electric impulses travel along neurones through nerve fibres (axon tail-thing)

Describe mammalian nervous systems in terms of CNS & PNS

• all mammals have:

  • a central nervous system (CNS)

  • a peripheral nervous system (PNS)

    • CNS AND PNS → coordinate + regulate body functions
      

• - CNS is coordinator and contains

  • - Brain

  • - Spinal cord

• PNS

  • Nerves

  • Receptors

function of CNS

Made of neurons obviously 

• - sorts through, processes and coordinates information

1. - receives electric impulses from receptors (through PNS)

2. - delivers the response electrical impulses to effectors along the correct nerve fibres...

described as the headquarters because it processes large amounts of information

The brain

• - receives incoming nerve impulses

• - processes and interprets information

• - makes decisions about the response!

after processing:

• - delivers vast quantities of electric impulses to effectors through the spine and PNS…

Spinal cord

• connects the brain to the PNS

• Basically the highway from PNS to brain

→ carries impulses:

• from receptors → to brain

• from brain → to effectors

• As the brain is NOT connected to the PNS… only the SPINE is.

• Spine also processes certain sensory info eg.

  • touch

  • pain

  • temperature

→ involuntary/ reflex actions: occur in spinal chord

• don't go through brain first

• Transmit response to brain and effectors at the same time!!

→ allows faster response which is important for survival. → like hot stove on hand

PNS

• nerves outside the brain and spinal chord

function:

• connects CNS to the rest of the body:

• allows communication between receptors and effectors

effectors = act on the response

receptors = detect stimuli through sense organs

Cranial nerves:

• - attached directly to brain

• - They control your sensory functions

• And sensory organs and like face movement

Pathway of nerve impulses from receptor to effector!

1) when receptor detects stimulus → it creates electric impulse

2) PNS → CNS

• - receptor detects stimulus (hot stove)

• - impulse travels through nerves to CNS

CNS

• - brain processes information that goes through spine,

• - Brain decides needed response (pain → act)

3) CNS → PNS

• - Brain sends impulse

• - Through spine again

• - along nerves

• - to effectors

• - effectors

• - → muscles contract

• - → glands secrete

3) Describe role of nervous system in coordination and regulation

• - nervous system coordinates into passing through body

• - regulates body function

coordination is receptors picking up stimuli and passing to effectors.

organisms need :

• - fast communication between receptors and effectors

• - so responses happen at correct times with correct effectors !

• - eg: touching something hot to immediate response.

endocrine vs nervous Communication:

• Nervous system: made up of neurons; 

• information transmitted in the form of electrical impulses; 

• impulses transmitted along nerve fibres (axons and dendrons); 

  • impulses travel very quickly;

  •  The effect of a nerve impulse usually only lasts for a very short time.

• Endocrine system: made up of secretory cells; 

• information transmitted in the form of chemicals called hormones; 

• chemicals carried dissolved in the blood plasma;

  •  chemicals travel more slowly; 

  • The effect of a hormone may last longer.

Structure of neurones:

• The human nervous system is made of cells! → NEURONES.

• - nerves - 

  • nucleus, cytoplasm, cell membrane

• - neurons have long fibres or cytoplasm from the cell body that allow them to carry impulses very quickly.

axon:

•  longest fibre

• - can be 1m long..

• - carries impulses away from cell body to other dendrites

-Dendrites:

• - shorter

• - pickup impulses from nearby neurones

• electric  impulse travel through neurones

Dendrites- cell body - along axon- to another neuron

ALL THIS TRANSMITS MESSAGES FROM RECEPTORS TO EFFECTORS

3 types of neurons: sensory, relay and motor

Sensory nerves

•  receptors on the end detect stimuli

• - receptors convert these to electric impulse

• - transmit to CNS

• - touch hot plate 

• receptor in finger detects stimulus and converts to electrical impulses

• - sensory neurone make electric impulse travel

• - impulse travels along sensory neurone to spinal cord

• Location: Found in receptors throughout the body, including the eyes, skin, and ears.

relay

• found in brain and spine (CNS)

• - relay pass the impulse to other neurones in the spine and brain

• - connect sensory neurones to motor neurones

• Rapid communication

• Location: Confined strictly to the brain and spinal cord.

motor

• - carry impulse from CNS to effectors

• - response impulse travels along neurone to muscle or glands

• - response- muscles contract and cause movement or glands secrete hormones

• Location: Cell bodies are within the CNS, but their axons extend outside to control muscles.

Describe a reflex arc

• Reflex arc pathway: Pathway along which nerve impulses passes

receptor → sensory neurone → relay neurone → motor neurone → effector- REFLEX ARC

Describe the sequence of a reflex arc

Stimulus:

• touching a hot plate

• Receptor:

• detects stimulus

• converts it into electrical impulse

• Sensory neurone:

  • carries impulse to spinal cord

• Relay neurone:

  • passes impulse within spinal cord

• Important:

• brain finds out later

• but response happens according to the  spinal cord first

• Motor neurone:

  • In CNS carries impulse to muscle or effectors

• Effector:

  • muscle contracts

  • finger moves away

Describe a reflex action and its importance

•  Reflex action:

  • - automatic

  • - rapid

  • - does not require conscious thought

• - "you don't think about it, brain finds out later"

-Define a reflex action (exam wording)

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

Explain the importance of reflex actions

Gets information from receptor to effector: as quickly as possible (ASAP)

• Saves time

•  and no need to think before acting

• Prevents injuries in organism

Example: withdrawing hand from hot object

Distinguish between voluntary and involuntary responses

• Reflex actions:

  • automatic

  • involuntary

• -Voluntary actions:

  •  under conscious control

  • e.g. reading

Sense organs

• groups of receptor cells

• detect specific stimuli

Describe different types of stimuli and their receptors

• Light:

  • eyes → vision

• Sound:

  • ears → hearing and balance

• Touch:

  • skin

• Temperature:

  • skin

• Chemicals:

  • nose → smell

  • tongue → taste

endocrine glands:

We know nerves carry electric impulses from 1 part of an animal to another…

• but we also use chemicals (hormones) to transmit info from 1 part of the body to another.

• Hormones travel blood or nerve impulses

hormones 

chemicals = hormones 

• (made in glands called endocrine glands)

• Glands release hormones directly into blood capillaries.

→ once hormone in blood, it's carried everywhere in body because dissolved in BLOOD PLASMA

• Although blood carries many hormones, each affects only certain parts of body = TARGET ORGANS

Hormone = chemical substance produced by gland

carried by blood

alters 1 or more specific target organs

and is then DESTROYED by liver'.

Types of Hormones

• - adrenal glands - adrenaline

• - pancreas - insulin

• - Testes - Testosterone

• - Ovaries - oestrogen

GLUCAGON SECRETED BY PANCREAS

Adrenaline

• 2 adrenaline glands: one above each kidney.

• make the hormone Adrenaline!

• when frightened or excited → your brain sends impulses along nerves to the  adrenal glands. = secreting adrenaline into blood.

adrenaline helps 'fight or flight' response by:

1. makes the heart beat faster,

   1. supplying O₂ to the brain & muscles more quickly for energy to fight or run away.

1. increases breathing

   1. so more O₂ can enter blood in lungs and gas exchange to occur faster. + more CO₂ exhaled

1. adrenaline widens pupils,

   1. allows more light to enter eyes which may help see danger more clearly.

1. blood vessels in skin & digestive system contract so they carry less blood,

   1. = makes you pale & 'butterflies in stomach' therefore as much blood needed in brain & muscles in an emergency.

1. also causes the liver to release glucose into blood.

   1. Produce extra glucose for muscles, so they can respire + more energy = for contracting and etc.

Homeostasis:

The environment of living is always changing! (eg. for us the weather outside vs inside)

maintenance of  the constant internal environment constant = [homeostasis!]

• Homeostasis helps cells work as efficiently as possible!

• Butttt, inside the cells of our body, everything is kept the same (more or less!) bc function best under specific conditions!

in the fluid around cells:

• temp constant

  • 37C is the constant temp: to help enzymes work at their optimum rate.

• amount of waterconstant

  • so cells not damaged by losing or absorbing too much H2O by osmosis

• concentration of glucose constant.

  • always enough fuel for respiration but never too much

WHO IS INVOLVED

• nervous system & various endocrine glands + skin, pancreas, liver involved in homeostasis

Control body temp:

• all mammals - and some birds - can keep body temp constant and controlled! (despite changing external temp!)

Skin layers

The most important organ involved in temp regulation = skin!

• Skin has 2 layers: 

  • Top = epidermis

  • Low = dermis

• All cells in epidermis have been made in a layer of cells at the base of the epidermis!

• These cells at base are always dividing, and new ones gradually move to the surface of skin.

• as they go up, they gradually die and fill with protein [KERATIN]

Top layer of Skin made of dead keratin cells = [CORNIFIED LAYER]

• The cornified layer protects softer, living cells underneath! bc = hard and waterproof.

• it's always being worn away and replaced by underneath cells!

• on parts of the body that get the most wear (soles of feet) it grows thicker!

Melanin

• some cells in epidermis have dark brown pigment = melanin!

• MELANIN = absorbs harmful UV rays in sunlight. 

• = These rays could've caused damage to living cells in deeper layers of skin.

Hair Follicles and sweat

• occasionally the epidermis folds inwards forming a hair follicle, one hair grows from each.

  • (hairs are made of keratin)

• sweat glands secrete liquid sweat! 

  • Sweat is water, salt, + urea (un poco)

• Travels in sweat ducts + onto the surface of skin through sweat pores.

  • sweat helps in temp regulation!!!

How to stay aware of your environment

• also blood vessels + nerve endings (receptors) that are sensitive to touch, pain, pressure + temp. 

  • Help you keep aware of changes in your environment

  • The receptors also change physical/chemical stimuli into electric impulses!

Fatty layer

• Beneath the skin is a layer of fat called adipose tissue.

• Fatty tissue contains cells that have large drops of oil.

• This layer helps insulate you against heat loss + acts as energy reserve...

Hypothalamus:

in brain - center of control mechanism that keeps internal temps constant CORE TEMP

• The hypothalamus coordinates activities of parts of the body that do temp change.

  • does this by having nerve ending/ temp receptors that sense if blood flowing through it is < 37c >

  • set point = 37c

  • If not, hypothalamus sends electric impulse along nerves

    •  to parts of bodies that have the function of regulating body temperature.

Temperature is below 37c

if temperature below 37c, electric impulse from hypothalamus:

1. make muscles from some parts of body contract/ relax very quickly: 

   1. This produces heat = SHIVERING

   2. This heat energy generated in muscles warm blood flowing through the muscle, the blood distributes this heat through the whole body…

1. hair erector muscles in skin contract, pulling hair up on ends.

   1. In humans this just gives us goose bumps

   2. Hairy animals, eg. cats, this hair standing traps a layer of warm air next to skin

   3. AND prevents skin from losing more heat - insulator.

arterioles that supply blood to capillaries near surface of skin become narrow/constricted = VASOCONSTRICTION

• Only little blood flows through, instead blood flows through shunt vessels in deep-lying capillaries, BLOOD STAYS WARM!!!

• This is because those vessels are under insulating fatty tissue (layer of fat adipose tissue insulate body!) ,

• so blood does not lose so much heat to the air

• = blue hands (Chloe!) 

Temperature over 37c

If temp over 37c... electric impulse from hypothalamus cause:

1. hair erector muscles to chill tf and relax, so hair lies flat on skin.

1. Sweat glands secrete sweat.

   1. sweat lies on the surface of hot skin

   2. water in sweat therefore evaporates, taking some heat too,

   3. thus cooling the body.
      

1. arterioles supplying capillaries with blood in surface skin become wider = VASODILATION...

   1. more blood flows close to the surface of skin …therefore…. heat lost from blood into air by radiation!!

blood vessels don't move in skin layers, they just get wide/narrow

Negative feedback

• The skin, muscles + hypothalamus keep control of internal body temp...

But you can't keep it 100% constant... you can only keep it within narrow limits.

When temp above 37c:

• hypothalamus senses and sends electric impulses to skin + muscles to respond to help cool the blood.

• When the body becomes too hot, cooling mechanisms start.

• When the blood becomes cool again, this information is fed back to the hypothalamus.

• The hypothalamus then stops the cooling responses and activates warming responses instead. (NEGATIVE
  

•  effect of action fed back to brain *

• info received stops action = negative

so all the time... hypothalamus monitors small changes in temp of blood and when rises above norm, works to lower, then when cold blood senses, stops cold actions and starts actions to raise blood temp.

•  feedback = when skin takes action to (get colder), the aftereffect information is FED BACK to hypothalamus, 

• after that, it is negative = because info about cooled blood makes hypothalamus tell skin to stop doing actions that do heat loss.

Importance of Control of blood glucose concentration

•  control of concentration of glucose in blood is very important for homeostasis

1. - cells need steady supply glucose to allow respiration (w/o this, they cannot release energy that they need)

1. - Brain cells are really dependent on glucose for respiration, and they die quickly if they are deprived of it!

1. Too much glucose in blood is not good,

   1. it can lead to craziness,

   2. it can cause H2O to leave cells by osmosis into blood,

   3. leads to not enough little H2O in cells to carry normal metabolic processes

Glucose concentration

•  control of blood glucose concentration is carried by pancreas + liver.

  • - Pancreas are 2 glands in one, 

  • 1 is ordinary glands with a duct.

    •  It makes pancreatic juice that flows through the pancreatic duct into duodenum for digestion. (small intestine...)

  •  scattered through pancreas are: groups of cells called ISLETS OF LANGERHANS

ISLETS OF LANGERHANS

- These cells do not make pancreatic juice; they make 2 hormones: INSULIN & GLUCAGON

• - These hormones → help the liver control the amount of glucose in blood.

• - Target liver:

Insulin

• Insulin - lowers blood glucose concentration

• eating increases glucose levels

•  respiration uses glucose

*if you eat a meal that has a lot of glucose, glucose absorbed through walls of the small intestine →

concentration of glucose in blood goes up.

• - Islets of Langerhans detect this rise and secrete insulin into blood.

  • when insulin reaches the liver, the liver absorbs glucose from blood.

  • Some glucose used for respiration,

  • but some made into insoluble polysaccharide | GLYCOGEN |

    • : stored in the liver.

Glucagon

Glucagon- Increases glucose concentration

if blood glucose concentration is too low…

•  pancreas secrete glucagon that cause liver cells to break down | GLYCOGEN |

• into glucose and release to blood

failure of this system = diabetes <3