Coordination and Chemical Coordination Notes

Coordination

  • Coordination links body activities to happen at the right time.
  • Involves the nervous system and the hormone/endocrine system.

Learning Objectives

  • Organisms respond to environmental changes.
  • Coordinated response requires a stimulus, receptor, and effector.
  • Central nervous system (CNS) consists of the brain and spinal cord, linked to sense organs by nerves.
  • Stimulation of receptors sends electrical impulses along nerves into and out of the CNS, resulting in rapid responses.
  • Describe the structure and function of the eye as a receptor.
  • Understand the function of the eye in focusing on near and distant objects, and in responding to changes in light intensity.
  • Describe the structure and functioning of a simple reflex arc, illustrated by the withdrawal of a finger from a hot object

Stimulus and Response

  • Stimulus: A change in an animal's surroundings.
  • Response: A reaction to that change.
  • Receptor: Detects the stimulus.
  • Effector: Produces an effect (e.g., muscles or glands).
  • Sequence: stimulus → receptor → coordination → effector → response
  • Nerve impulses are tiny electrical signals.

Receptors and Energy

  • Receptors detect stimuli by changing energy into electrical energy (nerve impulses).
  • Examples:
    • Eye (retina): light
    • Ear (hearing): sound
    • Ear (balance): mechanical (kinetic)
    • Tongue (taste buds): chemical
    • Nose (smell): chemical
    • Skin (touch/pressure/pain): mechanical (kinetic)
    • Skin (temperature): heat
    • Muscle (stretch): mechanical (kinetic)

The Central Nervous System (CNS)

  • Impulses travel along neurones (nerve cells).
  • Impulses are caused by movement of charged particles (ions).
  • Speed: 10-100 meters per second.
  • Sensory neurones carry impulses to the brain and spinal cord (CNS).
  • Motor neurones transmit impulses from the CNS to muscles and glands.

Structure of Neurones

  • Sensory and motor neurones can be very long.
  • Motor Neurone:
    • Cell body in the CNS with dendrons and dendrites.
    • Axon carries impulses to the effector organ.
    • Neuromuscular junction: synapse between nerve endings and muscle.
    • Myelin sheath: insulates the axon and speeds up conduction.
  • Sensory Neurone:
    • Cell body on a side branch of the fibre, outside the CNS.
    • Fibre from receptor to cell body is a dendron, from cell body to CNS is a short axon.

The Eye

  • Sclera: Tough outer coat, visible white part.
  • Cornea: Transparent "window" at the front, lets light in.
  • Iris: Coloured ring of tissue.
  • Pupil: Hole in the iris that lets light through.
  • Choroid: Dark layer under the sclera, prevents light reflection.
  • Retina: Light-sensitive layer with rods and cones.

Forming an Image

  • Refraction (bending of light) occurs at the cornea and lens.
  • Image on the retina is inverted.

Iris Reflex

  • Controls the amount of light entering the eye by changing pupil size.
  • Circular muscles contract, radial muscles relax: pupil constricts (bright light).
  • Radial muscles contract, circular muscles relax: pupil dilates (dim light).
  • Purpose: to allow the right intensity (brightness) of light to fall on the retina

Accommodation

  • Changes in the eye allowing focus on objects at different distances.
  • Lens shape is changed to adjust focus; more convex lens refracts light more.
  • Distant object:
    • Ciliary muscles relax, suspensory ligaments pulled tight, lens flattens.
  • Nearby object:
    • Ciliary muscles contract, suspensory ligaments slacken, lens bulges.

Chemical Coordination

  • Endocrine system: Coordination system using hormones.

Glands and Hormones

  • Gland: Organ that releases or secretes a substance.
  • Exocrine glands: Secrete products through a duct (e.g., salivary glands).
  • Endocrine glands: Ductless glands, secrete hormones into the bloodstream.

Differences Between Nervous and Endocrine Control

  • Nervous System:
    • Nerve impulses via nerve cells (chemicals at synapses).
    • Fast, instant effect.
    • Short-lived response.
    • Localised effect.
  • Endocrine System:
    • Hormones transmitted via bloodstream.
    • Slower, longer to act.
    • Longer-lasting response.
    • Widespread effects.

Endocrine Glands and Hormones

*Pituitary gland:
* ADH: controls the water content of the blood.
* FSH: stimulates egg development and oestrogen secretion.
* LH: stimulates egg release and testosterone production.
*Thyroid: Thyroxine, controls the body's metabolic rate.
*Pancreas:
* Insulin: Lowers blood glucose.
* Glucagon: Raises blood glucose
*Adrenal: Adrenaline, prepares the body for physical activity
*Testes: Testosterone, controls the development of male secondary sexual characteristics.
*Ovaries:
* Oestrogen: controls the development female secondary sexual characteristics.
* Progesterone: regulates the menstrual cycle

Adrenaline

  • Prepares the body for action.
  • Effects: increased breathing rate, faster heartbeat, diverted blood flow, glucose release, dilated pupils, increased mental awareness, body hair stands upright

Insulin

  • Made by pancreas, lowers blood glucose levels by stimulating liver cells to take up glucose and convert it into glycogen.
  • Diabetes: Pancreas cannot make enough insulin.
    • Type 1: pancreas not produce insulin
    • Type 2: Body shows insulin resistance