COORDINATION AND RESPONSE

Define homeostasis

Define homeostasis

Maintaining a constant internal environment despite external change.

State three conditions which need to be controlled within the body

• temperature

• Water levels

• Blood glucose concentration

What are the three main parts to a coordinated response?

• A stimulus, e.g. temperature change

• A receptor (to detect the change)

• An effector (To carry out the response)

What does auxin trigger?

auxin triggers growth of the main stem of the plant and inhibits the growth of side shoots.

What is phototropism in which part of a plant is positively phototropic?

Phototropism is the growth of a plant to delight source the shoots are positively phototropic they grow towards the Light source.

What is geotropism in which part of a plant is positively geotropic?

Geotropism is the growth of a plant towards the pool of gravity the roots are positively geotropic they grow down in the same direction as the pull of gravity.

How does auxin cause the shoot to grow towards the light source?

• Auxin on the shaded side

• Auxin promotes cell growth

• The shoot curves towards the light

Give three differences between nervous and hormonal communication

• nervous communication and uses nerve cells and impulses whereas hormones are secreted by glands and Travel in the blood

• Nervous communication, much faster than hormonal communication

• Communication usually brings long lasting Responses and nervous communication

What is the difference between the central nervous system and the peripheral nervous system?

The central nervous system is the brain and the spinal cord, whereas the peripheral nervous system is every other part of the nervous system.

How is an impulse transmitted between two neurons?

• The impulsive reaches the end of one neurone

• A neurotransmitter is released and diffuses across the gap

• A new impulse is triggered in the next neurone

What is a Stimulus?

A stimulus is a change in the environment.

What is an effector?

A part of the body that brings about the response to stimulus like a muscle or a gland.

Describe the reflex arc.

• Stimulus detected by receptor

• Impulse past along Sensory neuron to the central nervous system

• Impulse past along motor Neuron to effector

• Effector brings about the response

Describe the sequence of events involved in removing a hand away from a Hot flame

• Thermoreceptors in the hand to take the heat of the flame

• An impulse is sent along the sensory neurone

• The impulse passes through the relay neurons in the CNS

• The impulse then passes along motor neuron and triggers the muscle in the arm to contract hand away

What is the cornea and what is its function?

• transparent layer in front of the eye that protects the eye from damage

What is the iris and what is its function?

The coloured ring around the pupil and controls its diameter

What is the optic nerve and what is its function?

The nerve coming out of the back of the eye that sends signals to the brain

What is the function of the lens?

The lens focuses the light rays onto the retina

What is the retina and what is its Function?

Rena is the back part of the eye and it converts visual stimuli into electrical impulses.

What do the ciliary muscles and suspensory ligaments do?

They control the shape of the lens (accommodation)

How does the eye focus on near objects?

• Ciliary muscles contract and suspensory ligaments relax causing the lens to thicken

• Thicker lens causes light refract more

How does the eye focus on far away objects?

• Ciliary muscles relax and suspensory ligaments stretch, which makes the lens thinner

• Thinner lens causes light to refract less

How does the eye respond to bring light?

The iris contracts, making the pupil smaller and letting in less light

How does the eye respond to a lack of light?

The iris relaxes which makes the pupil larger and lets in more light.

Why does temperature need to be controlled

To provide a suitable environment for enzymes so that they can work fastest at their optimum temperature.

Give 2 processes involving the skin that cool the body down

• Sweating - evaporation → cools skin down

• vasodilation - allows blood to flow closer to the surface of the skin where it can cool

Give 3 processes that work to keep the body warm

• vasoconstriction

• Shivering

• Erection of hairs on the skin

Describe the process of vasoconstriction

• the body detects a drop in temperature

• Blood vessels supplying capillaries constrict + muscles in vessels contract

• Less blood flows closer to skin therefore less heat loss to surroundings

What are hormones?

They are chemical messengers that are secreted by the glands in the endocrine system.

What does insulin do to the body?

Decreases blood glucose levels

Where is insulin secreted from

Beta cells of pancreas

What does testosterone do?

• main male sex hormone

• Involved in growth of testes and penis

• Triggers many changes in males during puberty (e.g. hair growth, deeper voice, increased muscle mass)

Where is testosterone secreted from?

The testes

When is adrenaline secreted from?

During times of anxiety, fear or stress

Where is adrenaline secreted from?

The adrenal glands.

Give 3 effects of adrenaline in the body

• increases heart and breathing rate

• Increases blood glucose conc

• Dilates pupils

What does oestrogen do?

Causes uterus lining to thicken

Where is oestrogen secreted from?

Ovaries

What hormone does oestrogen inhibit?

FSH

What does progesterone do?

Maintain womb lining

Where is progesterone secreted from?

The ovaries

What hormone does progesterone inhibit?

LH and FSH

What does FSH do?

FSH stimulates the follicle to mature and release oestrogen.

What does LH do?

Causes the release of an egg from a follicle (ovulation)

Where is FSH secreted from?

Anterior pituitary gland

Where is LH secreted from

Anterior pituitary gland

Where is ADH secreted from?

The posterior pituitary gland