ANHB1102 Lecture 1: ANHB1102 study guide LECTURES/TEXTBOOK COMBINED WHOLE SEMESTER
29 May 2018
School
Course
Professor
ANHB1102
HUMAN BIOLOGY II – BECOMING HUMAN
BY ALYSSA SANTARELLI
2
TOPIC ONE: THE NERVOUS SYSTEM
Overview of the Nervous System:
There are two main divisions of the nervous system – the central nervous system
(CNS) and peripheral nervous system (PNS). Both the CNS and PNS contain
specialized cells that carry information and commands – neurons.
The Central Nervous System
The central nervous system is comprised of the brain and spinal cord. The brain
and spinal cord are enclosed by the cranium and vertebral column respectively,
and protected by the meninges. The meninges is made up of three layers:
1. The dura mater – the outmost, thickest layer
2. Arachnoid mater – the middle layer
that forms arachnoid granulations
that form projections for
cerebrospinal fluid to be reabsorbed
3. Pia mater – the thinnest, most
delicate layer that adheres to the
surface of the brain and spinal cord,
rich with blood vessels
Also protecting the central nervous system
is the ventricular system, containing cerebrospinal fluid (CSF). There are large
3
cavities present in the brain stem and cerebral hemispheres, which serve as a
channel for CSF. The CSF is primarily used for protection, chemical stability and
buoyancy.
The Peripheral Nervous System
The PNS is all of the nervous system except for the brain and spinal cord. It is
composed of two substances
1. Nerves – bundles of nerve fibers (axons) wrapped in a fibrous connective
tissue, and
2. Ganglia – knot-like swellings in a nerve where the cell bodies lie
The parasympathetic nervous system has two main divisions – the sensory
division and motor divisions. The sensory and motor divisions have further
subdivisions, the somatic (voluntary) and visceral (involuntary) subdivisions.
Sensory and Motor Divisions
The sensory division (called the afferent division) carries information from
receptors to the central nervous system. The somatic sensory division carries
signals from receptors in the skin, muscles, bones and joints while the visceral
sensory division carries signals from visceral organs (i.e. heart, lungs, stomach
and urinary bladder.)
The motor division (called the efferent division) carries signals from the CNS to
effectors, which are usually glands or muscles that carry out the body’s response.
The somatic motor division carries signals to skeletal muscles, which produces
muscular contraction and somatic reflexes. The visceral motor division carries
signals to glands, cardiac and smooth muscle, and their involuntary responses
are called visceral reflexes.
The Autonomic Nervous System
The visceral motor division of the peripheral nervous system is referred to as the
autonomic nervous system. It has parts present in both the CNS and PNS, making
it anatomically not a distinct division. Similar to the CNS and PNS, the autonomic
nervous system has an efferent and afferent component. The efferent component
sends signals to muscles and glands, and can cause an excitatory (sympathetic)
or inhibitory (parasympathetic) effect. The afferent component is largely
imperceptible as the sensations are all within normal limits. However, if there is
excessive pressure or stretch on visceral organs, warning signals felt as pain are
sent.
