Biology Class 10: Control and Coordination

Chapter 15: Control and Coordination

• 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.

Biology Meets Psychology

• 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.

Hormonal Communication

• 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.

Nervous Communication

• 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.

Neurones

• 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

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

Sensory Neurons

• Sensory neurons have a long axon with a cell body located near the stimulus.

Synapses

• 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

• 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.

Action Potentials

• 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.

How Neurones Work Together

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

Resting Potential

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

Action Potentials

• Action potentials are rapid, brief changes in electrical potential.
• Voltage-gated channel proteins open and close in response to potential changes.
• Sodium ions enter, and then potassium ions leave, creating an action potential.

Synaptic Transmission

• The process of transmitting impulses across the synapse.
• Neurotransmitters released from the presynaptic neuron into the cleft.
• These bind to receptor on the postsynaptic neuron, causing a response.

Muscle Contraction

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

Coordination in Plants

• 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.