Coordinationand response

CNS (Central Nervous system)

Composed of brain and spinal cord which contains relay neurons.

PNS (peripheral nervous system)

Composed of cranial nerves, spinal nerves, peripheral nerves which contains sensory neurons and motor neurons.

Sensory organs

Skin, eyes, nose, ears, and tongue

Coordinate response

• Stimulus

• Receptor

• Sensory neurons

• Relay Neuron

• Brain and spine

• Motor neurone

• Effector

• Response

neurons

Neurons are elongated cells, consisting of body and long, thin axon.

Dendrites

Extended from the cell body and connect with other neurons, allowing electrical impulses to pass from one to the other (make connection with other neurons)

myelin sheath

Insulating liquid that wrapped the axons which speeds up nerve impulse

Axons

Send the Nerve impulses across the cell

Cell body

Main system of the neurons

What are motor neurons?

Motor neurons transmit messages from the brain and spinal cord to the muscles and glands

What are sensory neurons?

Sensory neurons transmit messages from senses, receptors such as the eye or nose to the brain or spinal cord

What are reflexes?

Fast , automatic protective biological control systems that linked a stimulus to a response (protect from danger)

How does a reflex arc response happen?

Reflex reactions happen without you having to think about them - they are involuntary. This is because the central nervous system sends electrical signals to the muscle before the brain can pick up the message.

What is a synapse?

Function between to neurones across which electrical signal pass

The release of neurotransmitters

When a nerve impulse arrives at the end of one neurone it triggers the release of neurotransmitter molecules from synaptic vesicles.

Continuing the impulse

The neurotransmitters diffuse across the synaptic cleft and bind with receptors on the next neurone, triggering another impulse

Nerve Transmission – The synapse

What are the main structures of the eyes and their functions?

Iris reflex

Pupil response - Bright light

• Pupil constricted ( smaller)

• Circular muscles contract

• Radial muscles relaxed

Pupil response - dim light

• Pupil dilates (bigger)

• Circular muscles relaxed

• Radial muscles contracted

Accommodation of light - near/close

• Ciliary muscles contract

• Suspensory ligaments ‘slacken’ (become slack)

• Lens becomes FAT

• Light is refracted more (bent)

Accommodation of light - Far/distant

• Ciliary muscles relax

• Suspensory ligaments ‘tighten’ (become taught)

• Lens becomes FLAT

• Light is refracted less (bent)

What are hormones?

Chemical messengers release in the blood stream which target certain organ

What are the sources and roles of the following hormones? (Adrenaline, Insulin,Testosterone,Progesterone,Oestrogen)

The main differences between the hormonal and nervous system

Nervous system

• Speed of action : faster

• How is the signal transmitted :Electrical impulse signals along axon

• How long does the signal last :Shorter lived

Hormonal System

• Speed of action : Slower

• How is the signal transmitted : Chemical messenger in blood stream.

• How long does the signal last :Can last months or even years

What are the main types of stimuli that plants respond to?

Three types:

• Light

• Water

• Gravity

What is a tropism?

a growth movement in response to a stimulus.

Are there different types of tropisms?

• Light: phototropism

• Water: hydrotropism

• Gravity: geotropism

How do roots and shoots respond to stimuli?

Shoots:

• Shoots grow towards sunlight. They are

positively phototropic.

• Shoots grow away from gravity. They are

negatively geotropic.

Roots:

• Roots grow away from sunlight. They are

negatively phototropic.

• Roots grow towards gravity. They are

positively geotropic.

Positive phototropism

• Auxins produced in the shoot tip move to the shaded side of the plant

• The auxins cause the cells on the shaded side to elongate and get bigger

• Growth ( bends ) towards the light

Positive geotropism

• Gravity pulls the Auxin down towards the roots where they rest on the bottom side of the root structures.

• Auxins retard root cell growth

• Root cells elongation and growth is inhibited by Auxin therefore the other side of the root grows faster and the roots grow towards gravity.

• Gravity pulls the Auxin down towards the roots where they rest on the bottom side of the root structures.

Homeostasis

the maintenance of a constant internal environment. 

• Body water content

• Body temperature

Maintenance of internal body temperature

Body temperature is maintained at 36 degrees. The body loses heat when the environment is too hot, and retains heat when the environment is too cold. 

Role of skin in temperature regulation

Mechanisms to retain heat

• Basic insulation 

  • The fat layer in the skin acts as an insulator

  • Skin hair follicles stand up to trap a layer of air around the skin which is also an insulator 

• Shivering 

  • Increased metabolism in muscles increase heat circulation

• Vasoconstriction

  • Heat is carried in the blood 

  • If blood goes near the skin surface, then heat radiates out of the body

  • Constriction of the skin arterioles reduce the amount of blood flowing near the skin surface to retain heat in the blood 

Mechanisms to lose heat

• Sweating 

  • Sweat is a mixture of water, salt and urea 

  • Water evaporates from sweat which causes the skin (and body) to cool down

• Vasodilation

  • Dilation of skin arterioles increase the amount of blood flowing near the skin surface to allow more heat to radiate out of the body