EDEXCEL IGCSE BIOLOGY - (2J) COORDINATION IN HUMANS

(2.80) How and why do organisms respond to changes in their environment?

1) A stimulus-change in the environment

2) A response-the organism's reaction to the stimulus

3) To maintain survival and prevent injury.

(2.81) What is homeostasis?

The maintenance of a constant internal environment.

(2.81) What are the three main examples of homeostasis in the human body?

1) Blood Glucose level

2) Body water content

3) Body temperature

(2.82) What three components are required for a coordinated response?

1) Stimulus (change in environment)

2) Receptor (found in sense organs-detect the stimulus)

3) Effector (muscle or gland)

(2.82) What are the 2 types of coordinated response?

1) Voluntary; involving the brain OR

2) Reflex; not involving the brain

(2.86) What are the two main control systems in the body?

1) Nervous system

2) Hormonal system

(2.86) How do signals travel in nervous vs. hormonal systems?

Nervous: Electrical impulses through neurons.

Hormonal: Chemicals (hormones) through the bloodstream.

(2.86) What type of signal does the nervous system and hormonal system use?

Nervous System: Electrical, chemical at the synapses (neurotransmitters)

Hormonal System: Chemical

(2.86) Compare the speed of nervous vs. hormonal responses.

Nervous System: Very fast

Hormonal System: Slower

(2.86) Compare the duration of nervous vs. hormonal responses.

Nervous System: Short-term

Hormonal System: Long-term

(2.86) Compare the end point of nervous vs. hormonal responses.

Nervous System: Effector (muscle or gland)

Hormonal System: Target organ(s)

(2.87) What makes up the central nervous system, and how is it linked to sense organs?

1) Brain and Spinal cord

2) Peripheral nervous system linked to CNS by nerves (bundles of neurones)

(2.87) What are the 3 types of neurons?

1) Sensory neuron

2) Relay neuron

3) Motor neuron

(2.87) How is the speed of electrical impulse increased in a neuron?

Speed: increased by MYELIN SHEATHS (provide insulation to the axon, in turn increasing the speed of electrical impulse travelling along the neuron)

(2.88) How does stimulation of receptors in sense organs lead to rapid responses? What is the process from stimulus to the rapid response?

Process:

Stimulus → Receptor → Electrical impulse → Sensory neuron → Relay neuron in the CNS (spinal cord) → Motor neuron → Effector (muscle/gland)

(2.89) What are neurotransmitters?

Neurotransmitters are chemical messengers.

(2.89) What is a synapse?

A gap between 2 neurons.

(2.89) What is the role of neurotransmitters in the process from the pre-synaptic neuron to the post-synaptic neuron? (3 steps)

-The PRE-SYNAPTIC NEURON has vesicles, which contain neurotransmitters.

-They travel through the synapse and bind to receptors on the POST-SYNAPTIC NEURON.

-They can either lower or increase the possibility of the POST-SYNAPTIC NEURON firing an action potential.

(2.88) What are the sense organs for each of the 5 senses?

1) Sight (eyes)

2) Hearing (ears)

3) Touch (skin)

4) Taste (tongue)

5) Smell (nose).

Receptors: Found in sense organs; detect stimuli (e.g., light, sound).

(2.90) How does a simple reflex arc work, using the example of withdrawing a finger from a hot object? (6 points)

1) The STIMULUS-change in environment (the change in temperature with the hot object)

2) The RECEPTORS in skin cells detect the stimulus.

3) The SENSORY NEURONS send an electrical impulse to RELAY NEURONS in the CENTRAL NERVOUS SYSTEM.

4) The RELAY NEURONS pass an impulse to a MOTOR NEURON.

5) The MOTOR NEURONS pass an impulse to the EFFECTOR (muscle or gland)

6) The EFFECTOR contracts, pulling your hand away from the object.

(2.91) What is the structure and function of the eye as a receptor? (11 structures)

1) Ciliary Muscle: Controls the shape of the lens for focusing (accommodation).

2) Blind Spot: The area where the optic nerve leaves the eye; it has no rods or cones, so light here is not detected.

3) Vitreous Humour: A clear, jelly-like substance that maintains the shape of the eye and supports the retina.

4) Rods: Light-sensitive cells in the retina that detect low light (night vision).

5) Retina: The light-sensitive layer at the back of the eye that contains rods and cones.

6) Suspensory Ligaments: Connect the ciliary muscle to the lens and help control its shape.

7) Cones: Light-sensitive cells in the retina that detect color and work best in bright light.

8) Optic Nerve: Carries electrical impulses from the retina to the brain.

9) Iris: Controls the size of the pupil to regulate the amount of light entering the eye.

10) Pupil: The hole in the center of the iris that allows light to enter the eye.

11) Cornea: The transparent outer layer that refracts (bends) light into the eye.

(2.93) What happens when the body is too hot? (5 points)

-Sweat glands produce more sweat

-Heat is lost through evaporation

-Vasolidation; blood vessels near skin DILATE

-More heat is lost through radiation

-Pilorelaxation-hairs relax and lay flat

(2.93) What happens when the body is too cold? (5 points)

-Sweat glands product less sweat

-Less heat lost through evaporation

-Vasoconstriction; blood vessels near skin CONSTRICT

-Less heat lost through radiation

-Piloerection-goose bumps and hairs go erect, trapping an insulating layer of warm air

(2.92) How does the eye focus on near and distant objects, and what is this called?

ACCOMODATION

(Ciliary muscles and suspensory ligaments are antagonistic muscles)

Near objects:

-Ciliary muscles contract.

-Suspensory ligaments relax.

-Lens becomes fatter and more rounded.

Distant objects:

-Ciliary muscles relax.

-Suspensory ligaments contract.

-Lens becomes flatter and less rounded.

(2.92) How does the eye respond to changes in light intensity, and what is this reflex called?

PUPIL REFLEX

Bright light:

-Circular muscles contract

-Radial muscles relax

-Pupil becomes CONSTRICTED

Dim light:

-Circular muscles relax

-Radial muscles contract

-Pupil becomes DILATED

(2.94) What are the sources, roles, and 3 effects of adrenaline?

Source: Adrenal glands (above kidneys)

Role: Prepares body for fight or flight response

Effects:

1) Narrows arteries in small intestine (redirects blood from gut to muscles)

2) Raises blood sugar levels

3) Increases heart rate

(2.94) What are the sources, roles, and effects of insulin?

Source: Pancreas

Role: Regulates blood sugar levels

Effects: Lowers blood glucose (allows glucose to enter cells)

(2.94) What are the sources, roles, and effects of oestrogen?

Source: Ovaries

Roles: Builds up uterus lining

Effects: Builds up uterus lining, stimulates production of LH, inhibits production of FSH

(2.94) What are the sources, roles, and effects of testosterone?

Sources: Testes

Roles: Creates male secondary sexual characteristics

Effects: Broken voice, pubic hair, broadened shoulders

(2.94) What are the sources, roles, and effects of progesterone?

Sources: Ovaries

Roles and effects: Maintains uterus lining

(2.94) What are the sources, roles, and effects of ADH (anti-diuretic hormone)?

Sources: Hypothalamus

Roles: Controls water reabsorption in kidneys

Effects: High levels of ADH = concentrated urine (less water lost), Low levels of ADH = Diluted urine (more water lost)

(2.94) What are the sources, roles, and effects of LH (Luteinizing Hormone)?

Sources: Pituitary gland

Roles in FEMALES: Triggers ovulation and release of progesterone

Roles in MALES: Stimulates testosterone production

Effects in FEMALES: Maintains menstrual cycle

Effects in MALES: Supports sperm production

(2.94) What are the sources, roles, and effects of FSH (Follicle Stimulating Hormone)?

Sources: Pituitary gland

Roles in FEMALES: Stimulates egg maturation in ovaries

Roles in MALES: Stimulates sperm production

Effects: Essential for reproduction (ovulation and spermatogenesis)