The Nervous System (1) Flashcards
what is the CNS composed of ?
the brain and the spinal cord
what is the PNS composed of ?
the PNS is composed of nerves that connect the CNS with glands and sense organs
state what it is meant by the key term - neurotransmitters
neurotransmitters are chemical transmitters released from neurones in response to chemical signals
state what it is meant by the key term - cell process
the cell process are the long exertions that connect neurones to each other
state what it is meant by the key term - cell body
also called the ‘soma’, contains a nucleus and ribosomes for protein synthesis
state what it is meant by the key term - dendrites
dendrites are branched outgrowths which receive inputs
state what it is meant by the key term - dendritic spines
dendritic spines are knob-link outgrowths that increase the surface area of dendrites, and contain ribosomes
state what it is meant by the key term - axon
sometimes called the ‘nerve fiber’, is a long process extending from the ‘soma’ that carries output to target cells
what lengths can an axon range between ?
um to > 1 m
state what it is meant by the key term - initial segment
the initial segment is then ‘trigger zone’ of the nerve fiber
state what it is meant by the key term - axon collateral
the axon collateral is the structure that can carry signals ‘sideways’
state what it is meant by the key term - axon terminal
the axon terminal establishes synaptic contact with another structure
state what it is meant by the key term - varicosities
varicosities are bulging areas where the signal can be released from
neurones are wrapped in myelin, which is what ?
myelin is a 20 - 200 layers of modified plasma membranes
what is myelin made out of, in what two locations ?
- CNS - oligodendrocytes
2. PNS - Schwann cells
state what it is meant by the key term - axonal transport
to maintain structure and function, organelles must move > 1 m between the soma and the axon terminals - axonal transport
state, and explain, what the 3 functional classes of neurones are
- afferent neurones - convey information from tissue/organs to the CNS
- efferent neurones - convey information away from the CNS to effector cells
- interneurones - convey information within the CNS
explain the location of ‘afferent neurones’ (2 points)
- cell body and the long peripheral process of the axon are in the PNS
- only the short central process of the axon enters the CNS
explain the location of ‘efferent neurones’ (2 points)
- cell body, dendrites and a small segment of the axon are in the CNS
- most of the axon is in the PNS
state 4 facts about interneurones
- function as integrators and signal changers
- integrate groups of afferent and efferent neurones into reflex circuits
- lie entirely within the CNS
- account for > 99 % of all the body’s neurones
what percentage of the CNS is made out of neurones, and what takes up the other 90 % ?
- Neurones = 10%
2. Glial cells = 90%
what percentage of the CNS space do neurones take up, and why ?
because neurones branch extensively, they occupy about 50% of the space within the CNS
what is the function of glial cells ?
glial cells surround the soma, axon, dendrites and provide physical and metabolic support to neurones
state the 2 functions of - Astrocytes
- regulate extracellular fluid by removing potassium and neurotransmitters
- stimulate epithelial cells to form junctions (blood-brain barrier)
state the function of - Micro-Glial cells
specialised macrophage like cells
state the function of - Ependymal cells
sit within fluid filled cavities, regulate the flow of cerebrospinal fluid
what are the two sub-divisions of the PNS ?
the Afferent division and the Efferent division
what is the Afferent Division of the PNS made up of ?
- somatic sensory
- visceral sensory
- special sensory
what is the Efferent Division of the PNS made up of ?
- somatic motor
2. autonomic motor (sympathetic, parasympathetic, enteric)
state what it is meant by the key term - Pathway/Tract
a group of neurones travelling together in the CNS is called a Pathway/Tract
state what it is meant by the key term - Commissure
if a group of axons link the L+R sides of the CNS, it’s called a commissure
state what it is meant by the key term - Ganglia
the cell bodies of neurones with similar functions within the PNS are called Ganglia
state what it is meant by the key term - Nuclei
the cell bodies of neurones within the CNS are called Nuclei
state what it is meant by the key term - a nerve
a group of many axons travelling together to and from the same general location in the PNS in called a nerve
are there nerves within the CNS ?
there are NO nerves within the PNS
the brain contains 4 interconnected cavities which are filled with what ?
cerebral ventricles
what is the largest component of the forebrain, and what does it consist of ?
the Cerebrum, and it consists of the L+R hemispheres
what is the central core of the forebrain ?
the central core of the forebrain is the Diencephalon
the cerebral hemispheres consist of what ?
the Cerebral Cortex (an outer shell of grey matter, giving the brain its grey appearance)
the inner cerebral cortex is what ?
the inner cerebral cortex is a layer of white matter (mainly myelinated fiber tracts)
what is within the grey matter, and what is the function of it ?
- subcortical nuclei
2. play an important role in movement/posture (basal nuclei most prominent)
each cortex is separated by a deep longitudinal division, but is connected by what ?
the ‘Corpus Collosum’
state the names, and function, of the two cell types in the cerebral cortex
- Pyramidal cells - major output
2. Non-Pyramidal cells - major input
the cerebral cortex is the integrating centre of the CNS. state 2 facts to support that statement
- basic afferent information is processed into meaningful perceptual images
- control over the systems that govern the movement of the skeletal muscle is refined
the Diencephalon (part of the forebrain) consists of what 3 structures ?
- Thalamus
- Hypothalamus
- Epithalamus
state 4 facts about the Thalamus
- a collection of several large nuclei
- play a role in general arousal
- controlling movement/posture
- focussing attention
state 2 facts about the Hypothalamus
- only 1% of total brain mass
2. homeostatic regulation of the internal environment
state 1 fact about the Epithalamus
controls biological rhythms (via the pineal gland)
state what 2 things the Hypothalamus controls
- behaviours having to do with the preservation of the individual
- behaviours having to do with the preservation of the species
what structure does the hypothalamus lie directly above ?
the hypothalamus lies directly above the pituitary gland - an important endocrine structure that the hypothalamus regulates
what is the main function of the Cerebellum ?
does not initiate voluntary movements, an important centre for the co-ordination of movements, and controlling posture and balance
where does the Cerebellum receive input from ?
receives information from the muscles and joints, skin, eyes, ears and the parts in the brain involved in the control of movements
what very important structure is within the Brainstem ?
within the Brainstem is the ‘Reticular Formation’ - the only part of the brain absolutely essential for human life
the brainstem receives and integrates information from all regions of the CNS and is involved within what 3 functions ?
- motor functions
- cardio-vascular and respiratory control, and swallowing
- regulates sleep, wakefulness, attention and eye movement
what bone structures protect the CNS ?
Cranium (brain) and Vertebrae (spinal cord)
state what it is meant by the key term - Meninges
Meninges are the membranes that line the structures and add additional support and protection
what are the 3 Meninge structures ?
- Dura mater
- Arachnoid mater
- Pia mater
state the 4 functions of the Meninges
- to cover and protect the CNS
- to protect blood vessels and enclose the venous sinuses
- contain cerebrospinal fluid
- from partitions in the skull
state what it is meant by the key term - Cerebrospinal Fluid (CSF)
cerebrospinal fluid (CSF) protects and cushions the structures within the CNS (made by the choroid plexus)
state what it is meant by the key term - Blood-Brain Barrier
the blood-brain barrier is a protective mechanism that hooks maintain a stable environment for the brain
state 2 additional facts about the blood-brain barrier
- these capillaries are the least permeable in the body; a very selective barrier
- substances that are highly lipid-soluble cross easily
what are descending and ascending tracts ?
- ascending tracts transmit information to the Brian
2. descending tracts relay information from the Brain to the spinal cord
grey matter is composed of what 4 structures ?
- interneuroens
- cell bodies
- entering axons of afferent neurones
- glial cells
what are Dorsal Horns and Ventral Horns ?
- grey matter projecting towards the back of the body = Dorsal Horns
- grey matter oriented towards the front = Ventral Horns
what matter surrounds what, and consists of what ?
white matter surrounds grey matter and consists of myelinated axons
what can peripheral nerves contain ?
peripheral nerves can contain nerve fibres that are the axons of efferent neurones, afferent neurones, or both
state 3 facts about the Somatic NS
- consist of a single neurone between the CNS and skeletal muscle cells
- Innervates skeletal muscles
- can only lead to muscle excitation
state 3 facts about the Autonomic NS
- has a two-neurone chain (connected by a synapse) between the CNS and the effector organ
- innervates smooth muscle, cardiac muscle, glands and GI neurones
- can be excitatory or inhibitory
what is the Enteric NS
the Enteric NS is a sub-division of the Autonomic NS, that innervates the neurones in the GI tract
explain the structure of the Autonomic NS (5 structures)
- CNS
- pre-ganglionic fiber
- ganglion
- post-ganglionic fiber
- smooth/cardiac muscle, glands, GI neurones
where do sympathetic neurones and parasympathetic neurones exit the CNS from ?
SNS - leave CNS from Thoracic and Lumbar vertebrae
PNS - leave the CNS from the Brainstem and the Sarcal vertebrae
what is the location of the sympathetic and parasympathetic ganglia ?
SG - close to the spinal cord (sympathetic trunks)
PG - within, or close to, the organs they innervate
what does the Sympathetic NS usually respond to ?
a single unit
what does the Parasympathetic NS usually respond to B
tends to activate specific organs in a pattern finely tailored to each physiological situation
state what it is meant by the key term - dual innervation
some tissues can be activated by both the Sympathetic and Parasympathetic nervous systems - dual innervation
if the sympathetic NS is ‘Fight or Flight’, then what is the Parasympathetic NS ?
‘Rest or Digest’ - homeostatic processes that are predominant
