Nervous & Endocrine Systems: Coordination and Control
Coordination Systems
Nervous System
Composed of nerve tissue, it prepares rapid, short-lasting responses. It acts through nerve impulses propagating along nerves.
Endocrine System
Composed of endocrine glands, it prepares slow, but durable responses. It acts through chemical messengers called hormones that travel through the blood to target cells or organs.
Elements of Coordination
Receptor
A structure that perceives stimuli and transmits them to nerve centers. Sensory organs are receptors that pick up stimuli from outside the body.
Stimulus
Any internal or external change capable of provoking a response from the body.
Nervous Center
Responsible for receiving information from receptors, processing it, and transmitting responses to effector organs.
Effector
Carries out the response. Two types of effectors produce two different responses:
- Muscle: Produces a motor response, involving movement.
- Gland: Produces a secretory response, involving the secretion of a substance.
Nervous System Components
The nervous system consists of cells called neurons.
Neuron Structure
- Axon: A long extension covered in myelin, which facilitates nerve impulse transmission.
- Cell Body (Soma): The main part of the neuron.
- Dendrites: Short, branched extensions of the cell body that receive signals.
Neurons receive and transmit signals through nerve impulses. The impulse travels from dendrites, through the neuron, and down the axon. Neurons communicate across synapses using neurotransmitters. When an impulse reaches the axon terminal, neurotransmitters are released into the synapse, triggering a new impulse in the next neuron.
Types of Neurons
- Sensory Neurons: Carry information from receptors to the central nervous system.
- Motor Neurons: Send information from the central nervous system to effectors.
- Interneurons (Association Neurons): Connect sensory and motor neurons.
Divisions of the Nervous System
The nervous system analyzes internal and external stimuli and develops necessary responses. It has two main divisions:
- Central Nervous System (CNS): Controls the body and its activities. Consists of the brain and spinal cord, protected by the skull and spine respectively.
- Brain: Divided into two hemispheres with a convoluted surface. The cerebral cortex (gray matter) contains neuron cell bodies and dendrites. The inner white matter consists of myelinated axons.
- Cerebrum: Responsible for higher-level functions.
- Cerebellum: Coordinates voluntary movements and balance.
- Medulla Oblongata: Controls involuntary functions like heartbeat and breathing.
- Spinal Cord: Extends from the skull base to the lower back, containing gray and white matter.
- Brain: Divided into two hemispheres with a convoluted surface. The cerebral cortex (gray matter) contains neuron cell bodies and dendrites. The inner white matter consists of myelinated axons.
- Peripheral Nervous System (PNS): Transmits impulses between receptors and the CNS, and from the CNS to effectors. Consists of cranial and spinal nerves.
- Sensory Nerves: Transmit information from receptors to the CNS.
- Motor Nerves: Conduct information from the CNS to effectors.
Further divided into:
- Somatic Nervous System: Controls voluntary body movements.
- Autonomic Nervous System: Controls involuntary functions. Subdivided into the sympathetic (activity) and parasympathetic (rest) systems.
Endocrine System
This system consists of endocrine glands that secrete hormones directly into the bloodstream. Hormones act on specific target cells or organs, producing slower but longer-lasting responses than the nervous system.