Nervous and Endocrine Systems: Functions and Structures
The Nervous and Endocrine Systems
Interaction: Basic Life Process
The basic life process of interaction consists of a series of functions which help the body to:
- Adapt to change
- Coordinate different systems
There are two systems involved in this process:
- Nervous system
- Endocrine system
The Nervous System
The nervous system is responsible for:
- Interpreting information received from the sensory organs
- Working out appropriate responses to this information
- Sending instructions to the effectors
- Coordinating the functions of the body’s organs
- Carrying out intellectual and mental processes
- Transmitting emotions and feelings
Neurons: Building Blocks of the Nervous System
Neurons are not isolated; they work together in groups. There is a small gap between the axon terminals of one neuron and the dendrites of an adjacent neuron. This gap is called a synapse. A synapse is a small gap between two neurons which is crossed by a nerve impulse.
Nerve pathways can be divergent or convergent.
Types of Neurons
- Sensory neurons
- Motor neurons
- Interneurons (these connect sensory and motor neurons)
Parts of a Neuron
- Cell body
- Axon
- Dendrites
The Central Nervous System (CNS)
The central nervous system is divided into two parts that work closely together:
- Spinal cord
- Brain
It is composed of:
- Grey matter
- White matter
The Spinal Cord
The spinal cord is a cylinder of nerve tissue.
- It produces reflexes.
- It carries sensory nerve impulses to the brain and motor nerve impulses from the brain to the effector organs.
The Brain
Brain Stem
The brain stem is the part of the brain which is connected to the spinal cord. It controls vital body functions like heartbeat and blood pressure. The brain stem helps regulate sleep and body temperature.
Cerebellum
The cerebellum is at the back of the brain. It coordinates motor impulses sent by the brain.
Cerebrum
The cerebrum is the largest part of the brain. Its interior is made of white matter, and its exterior, a thick layer called the cerebral cortex, is made of grey matter. The cerebrum is divided into two hemispheres.
Summary of Brain Functions
- It processes information from sensory organs.
- It works out responses to stimuli and sends out appropriate commands to effectors.
- It regulates the functions of every part of the nervous system.
- It controls advanced functions like memory, reasoning, intelligence, conscience, and will.
The Peripheral Nervous System (PNS)
The peripheral nervous system is all of the nervous system that is outside of the brain and spinal cord.
Structure of the Peripheral Nervous System
- Sensory receptors
- Sensory nerves
- Motor nerves
- The somatic (or voluntary) nervous system
- The autonomic (or involuntary) nervous system
The Somatic Nervous System
The somatic nervous system consists of all the sensory nerves, motor nerves, and mixed nerves for the external sensory organs and for voluntary muscle movement.
Cranial Nerves
There are 12 pairs of cranial nerves that enter and leave the brain.
Spinal Nerves
Spinal nerves emerge from the spinal cord. There are 31 pairs of mixed nerves.
The Autonomic Nervous System
The autonomic nervous system is responsible for regulating and controlling involuntary body functions.
- Sympathetic nervous system
- Parasympathetic nervous system
Reflexes
Reflexes are quick, automatic actions that happen when a rapid response is required. Voluntary actions are slower and more elaborate than reflexes.
The Endocrine System
Glands are organs that produce and secrete hormones to control body processes. The endocrine system is a group of special glands (endocrine glands) that release hormones directly into the bloodstream.
The Endocrine Glands and Their Hormones
- Pituitary gland:
- Vasopressin
- Oxytocin
- Stimulating hormones
- Growth hormone
- Thyroid gland
- Parathyroid glands
- Adrenal glands:
- Adrenaline
- Corticosteroids
- Pancreas:
- Insulin
- Glucagon
- Testicles: Androgens
- Ovaries: Oestrogens