Functions of the Nervous System
- Sensory input
- Information gathered by sensory receptors about internal and external changes
- Integration
- Processing and interpretation of sensory input done by brain or CNS
- Motor output
- Activation of effector organs (muscles and glands) produces a response
Organization of the Nervous System
The nervous system can be divided into two parts.
- The central nervous system (CNS) consists of the brain and the spinal cord.
- The peripheral nervous system (PNS) consists of sensory (afferent) neurons and efferent neurons.
Neurons can be classified according to their function
SENSORY (AFFERENT) NEURONS
- - Neurons carrying information TOWARD the CNS, are Sensory Neurons
- Transmit impulses from sensory receptors toward CNS
- Almost all are Unipolar
- Cell bodies in ganglia in PNS
- Most cell bodies in CNS (except some autonomic neurons
- Neurons carrying information AWAY from the CNS, are Motor Neurons
- Carry impulses from CNS to effectors which are glands or muscles that carry out the commands of the CNS
- If a neuron connects a sensory neuron to a motor neuron in the CNS, it is an Interneuron.
- Interneurons are sometimes called association neurons
- most are entirely within CNS
- Lie between motor and sensory neurons
- Shuttle signals through CNS pathways; most are entirely within CNS
Divisions of the Nervous System
Two Main Divisions of the Nervous System
The nervous system is divided into the
The nervous system is divided into the
- Central nervous system (CNS) -
- The CNS includes the brain and spinal cord
- Peripheral nervous system (PNS) -
- The PNS includes everything outside of the CNS
The Peripheral Nervous System is further divided into the
- Sensory (Afferent) Division - input
- Motor (Efferent) Division - output
The Motor Division of the Peripheral Nervous System is subdivided into the
- Somatic nervous system – conscious control / voluntary
- Autonomic nervous system - unconscious / involuntary
The Autonomic Nervous System is Subdivided into:
- Sympathetic Nervous System
- Parasympathetic Nervous System
The Sympathetic Nervous System controls the body's fight or flight responses;
The Parasympathetic Nervous System governs the body's rest and digest responses
- releases adrenaline (epinephrine)
- pupils dilate
- increases heart rate
- increases rate of respiration
- releases additional glucose into the bloodstream
- inhibits digestion and inhibits urination
The Parasympathetic Nervous System governs the body's rest and digest responses
- pupils constrict
- slows heart rate
- decreases rate of respiration
- promotes digestion and urination