Biology Chapter: Coordination and Response

Coordination and Response

• The nervous system and endocrine system are essential for coordination in the body.
• Receptors detect stimuli (changes in the environment).
• Effectors carry out responses to maintain homeostasis.

Key Points

• Voluntary actions are under conscious control.
• Involuntary actions are automatic (e.g., reflexes).
• Synapses are junctions between neurons.
• Neurotransmitters carry signals across the synapse.
• Neurotransmitters are stored in synaptic vesicles.
• The synaptic cleft is the space between neurons.
• Receptor molecules on the receiving neuron bind to neurotransmitters.
• Reflex arcs ensure impulses travel in one direction.
• Drugs like heroin affect synapses.

Coordination System: The Nervous System

• The central nervous system (CNS) consists of the brain and spinal cord.
• The peripheral nervous system (PNS) connects the CNS to the rest of the body.
• Impulses are received by receptors and transmitted to the CNS.
• The CNS processes the information and sends signals to effectors.
• The nervous system controls many functions like movement and responses.

Coordination System: The Endocrine System

• Involved in communication and coordination within the body.
• Works by releasing hormones into the bloodstream.
• Hormones regulate various bodily activities and processes.

Sense Organs

• Groups of receptor cells that respond to specific stimuli.
• Examples include receptors in the eyes, ears, and skin.

Spinal Cord

• Conducts impulses from the brain to the effectors below the neck.
• Controls reflex actions below the neck.
• Carries impulses from sense organs below the neck to the brain.
• Consists of nerve cells and supporting tissues.
  • Has a front and back, containing spinal nerves.
  • Contains nerves that send and receive messages.

The Neuron

• The basic unit of the nervous system.
  • Sensory neurons transmit impulses from sensory receptors to the CNS.
  • Motor neurons carry impulses from the CNS to effectors.
  • Relay/interneurons connect sensory and motor neurons within the CNS, processing information.
• The neuron consists of a cell body, axon, and dendrites.

Myelin Sheath

• Layers of fat that cover the axons of some neurons.
• Increases the speed of impulse transmission.
• Nodes of Ranvier are gaps in the myelin sheath.

Synapse

• Junction between two neurons.
• Impulses are transmitted across the synapse through neurotransmitters.
• Neurotransmitters are chemicals stored in synaptic vesicles in the axon terminals.
  • Neurotransmitters diffuse across a synaptic cleft.
  • Neurotransmitter has to be removed from the gap.

Nerve Impulse Transmission

• Electro-chemical signals travel down nerve fibres.
• Ganglia contain the cell bodies of sensory neurons.
• Ganglia are a swelling in the sensory neuron, containing the cell bodies. They adapt to their functions and have long axons and dendrons. They have dendrites to receive impulses from other cells and myelin sheath.
• Neurotransmitters diffuse across the synaptic cleft in a one-way direction activating the post-synaptic membrane.

Reflex Action

• Rapid, involuntary response to a stimulus.
• Does not involve conscious thought.
• Important for survival and learning.

Reflex Arc

• Pathway of impulses in reflex action.
• Receptors detect a stimulus.
• Impulses travel along sensory neurons to the spinal cord or brain (dorsal root).
• Impulses pass through relay neurons in the CNS.
• Impulses travel along motor neurons to effectors (ventral root).
• Effectors carry out the response.