Biology Class 10: Control and Coordination

Study Notes

Learning Intentions:
- Describe the endocrine system, using examples like insulin, glucagon, and ADH.
- Compare how mammals use the endocrine and nervous systems to respond to internal and external stimuli.
- Describe sensory and motor neurons, and explain how they function.
- Explain the function of intermediate neurons.
- Explain the role of sensory receptor cells, using a chemoreceptor in a taste bud as an example.
- Describe and explain nerve impulse transmission.
- Describe and explain the structure and function of cholinergic synapses.
- Describe the ultrastructure of striated muscle and how muscle contracts in response to impulses from motor neurons.
Before you start:
- Make a list of the roles that membrane proteins play. This should be discussed with others.

Humans have five senses (touch, sight, hearing, taste, and smell).
Some believe in extrasensory perception (ESP); research suggests that we detect subtle changes which can’t be put into words, so we imagine extra senses.
Some have synaesthesia: a condition where one sense triggers another (e.g., hearing a note and seeing a colour).
A neurological case of a woman losing sense of having a body illustrates the importance of sensory feedback from muscles and joints for coordination.
Researcher Wilder Penfield's work on epilepsy patients explored brain areas involved in specific functions.
Ethics of experimenting on the nervous system of people during research.

Animals and plants coordinate the activity of their parts.
Endocrine system : contains ductless glands that release hormones directly into the blood.
Examples of endocrine glands include the pituitary, islets of Langerhans, adrenal, testes, and ovaries.
Some hormones (e.g., insulin, glucagon, ADH) control homeostasis.
These hormones may have far-reaching effects or relatively local.
Different hormone types affect specific cells and actions in the body.

The nervous system is made of the central and peripheral nervous systems.
The CNS contains the brain and spinal cord while the PNS contains cranial and spinal nerves.
Nerves contain many nerve cells.
Nerve cells are also called neurons and transmit nervous impulses.

There are three types of neurons; each with a specific function:
- Sensory neurons transmit impulses from receptors to the CNS
- Motor neurons transmit impulses from the CNS to effectors.
- Intermediate/relay neurons are entirely within the CNS, connecting sensory and motor neurons.

Motor neurons carry impulses from the brain or spinal cord to muscles or glands.
Contain a cell body with dendrites and an axon.

At synapses, impulses are conducted from one neuron to the next by releasing neurotransmitters.
The synaptic cleft is the gap between two neurons.
Acetylcholine is a neurotransmitter released in cholinergic synapses.

Myelin surrounds axons in motor and sensory neurons.
Myelin is produced by Schwann cells.
Myelin increases the speed of nerve impulses.
Nodes of Ranvier are gaps in the myelin sheath which allow nerve impulses to move quickly.

An action potential is a rapid change in electrical potential difference across a neuron's membrane.
They are caused by the movement of sodium and potassium ions.
The refractory period is a short interval after an action potential during which another action potential cannot be generated.

Reflex actions can be coordinated by nerve pathways without conscious brain involvement.

Resting potential is the electrical potential difference across a neuron's membrane when it's not transmitting an impulse.

Striated muscles are composed of muscle fibres, each with myofibrils and filaments (myosin, actin).
Muscles contract through processes which happen in the sarcomeres.

Plant hormones (also called plant growth regulators), interact with receptors to control growth and responses to stimuli.
Plants respond to gravity, water, light, and other environmental changes through hormonal action.