worksheet answers Flashcards
What is the reason for having a very convoluted brain, i.e. many sulci and gyri?
Larger surface area means a greater volume of grey matter, which in the cerebrum consists of
billions of interneurons
. Describe the distribution of white and grey matter in the different brain areas, including the
spinal cord. What do they represent?
Cerebrum: grey matter on the outside (cortex), white matter more internal (tracts connecting
different brain areas)
Midbrain, pons and medulla: Mostly white matter (various tracts, e.g. pyramidal tracts) with some nuclei (grey matter)
Spinal cord: “Butterfly” structure of grey matter in the centre with anterior (motor neuron cell
bodies) and posterior horns (sensory neuron cell bodies) and interneurons; white matter around
(motor and sensory tracts)
What are the layers of the meninges? What are the subdural and subarachnoid spaces?
Dura mater = periosteal and meningeal layer, contains venous sinuses
Arachnoid = very fine connective tissue with fibres anchoring to pia mater
Pia mater = follows all the gyri into sulci
Subdural space = between dura and arachnoid, filled with fluid
Subarachnoid space = between arachnoid and pia, contains larger arteries and veins
areas of cerebral hemisphere
Primary motor cortex
(precentral gyrus)
Primary sensory cortex
(postcentral gyrus)
Primary visual cortex
Broca’s area
Wernicke’s area
Prefrontal cortex
Primary motor cortex
precentral gyrus
Large motor neurons (pyramidal cells); voluntary
muscle movement
Wernicke’ area
Understanding written and spoken language
Primary visual cortex
Interprets visual stimuli
Primary sensory cortex
postcentral gyrus
Receives information from somatic receptors in the
skin and proprioceptors
brocas area
Motor speech area, directs muscles that are
involved in speaking, also active when we think
about what we want to say
Prefrontal cortex
Intellect, personality, working memory, abstract
thinking
basal nuclei
Grey matter deep within cerebrum; involved in
motor function in coordination with substantia nigra
and cerebellum
corpus callosum
White matter; tracts connecting both hemispheres
areas of the diencephalon
Thalamus
Hypothalamus
Pituitary gland
Pineal gland
thalamus
Relay station for all information coming into the
cortex; sorted, edited and integrated
hypothalamus
Regulates homeostasis (temp, sleep, food, etc.)
pituitary gland
Releases hormones to control endocrine system
pineal gland
Secretes melatonin which induces sleep
areas of the brainsem
Midbrain with
substantia nigra
Pons
Medulla oblongata and
pyramids
midbrain and substantia nigra
White matter (pyramidal tracts) and some nuclei,
e.g. substantia nigra; involved in reflexes (startle
and visual) and RAS; substantia nigra produces
dopamine; exit point of cranial nerves
Note: RAS = reticular activation system
medulla oblongata and pyramids
Top part of spinal cord; white matter (pyramidal
tracts in the pyramids); nuclei that are part of RAS;
cardiovascular and respiratory control; vomiting
and swallowing centre; sneeze and cough
reflexes; exit point of cranial nerves
pons
White matter, some nuclei, respiratory control, exit
point of cranial nerves
.When you feel tired during a long drive, you could open the window, sing along with the radio,
pinch yourself and have some cold water. How does this affect your alertness?
Increasing the amount of sensory input will activate the RAS (reticular activation system). The
more different stimuli that will be processed in various brain regions, the more effective this is.
Here you have skin sensation from the open window (wind and cold), auditory stimuli (music) and
activated taste receptors (cold water).
However, sleep can override the RAS, particularly if you are sleep deprived, so this is not always
working.
Explain how cerebrospinal fluid is formed and describe its movement
Made by filtration in choroid plexuses in the ventricles; circulates through ventricles and in
subarachnoid space; lateral ventricles → third ventricle → fourth ventricle → through apertures
into subarachnoid space and also into central canal along the spinal cord
- What channels in the presynaptic neuron open up in response to an action potential?
Voltage-gated Ca2+ channels
The presence of what ion inside the cell causes the synaptic vesicles to fuse with the
membrane?
Ca2+
Name six common neurotransmitters and whether they are excitatory or inhibitory
Acetylcholine (Ach) – can be both, very common in CNS and PNS
Noradrenaline – can be both, also in CNS and PNS
Dopamine – both, substantia nigra and other areas of CNS (“feel good” neurotransmitter
Serotonin – inhibitory, CNS (plays a role in mood, appetite, sleep)
GABA – main inhibitory, in CNS
Glutamate – main excitatory, in CNS
Describe the release and action of neurotransmitters
Neurotransmitters are stored in vesicles in the axon terminals. Ca2+ entering the axon due to an
AP causes the vesicles to fuse with the presynaptic cell membrane and release them into the
synaptic cleft.
They diffuse across and bind to receptors at the postsynaptic cell membrane. This triggers a
graded potential which can either lead to or prevent an AP.
How are neurotransmitters removed from the synaptic cleft?
They can be pumped back into presynaptic terminals (e.g. serotonin), broken down by enzymes
(e.g. Ach) or diffuse away.
Name three factors that can enhance transfer of information from short-term into long-term
memory
Practice and rehearsing
Being excited about the new information/task and having positive feelings
Being able to associate new information with previously learned facts and skills
Sleep enhances memory consolidation
Describe the stages of sleep and the order in which you progress through them during a
typical night. You can also draw this if you want.
REM sleep = rapid eye movement, often coincides with dreaming, high brain activity and muscles
paralysed
Non-REM stages 3 and 4 are deep sleep, showing delta waves
Where is the limbic system located and what is its role?
Various brain parts are involved, especially deep cerebral areas and parts of the diencephalon,
e.g. hippocampus, amygdala and other nuclei. This functional system regulates emotional
behaviour, such as reaction to stress or threats, aggression, etc. It is closely linked to the
olfactory (smell) areas.
When would you see delta waves, when alpha waves?
Delta = during deep sleep Alpha = quietly alert, relaxed with eyes closed
. Describe the pathway for a sensory (afferent) stimulus from the receptor to the primary
sensory cortex.
First order neuron: Receptor = mechano-, thermo-, photo-, chemoreceptors or nociceptor →
distal branch of sensory neuron via peripheral and then spinal nerve (cell body is in dorsal root
ganglion) → proximal branch of neuron via dorsal root into dorsal horn
Second order neuron: Interneuron in dorsal horn → crosses over to the opposite side and axon
goes all the way to thalamus
Third order neuron: Cell body in thalamus → primary sensory cortex and other higher centres
(photoreceptor would send information to primary visual centre)
Describe the motor (efferent) pathway from the primary motor cortex to a muscle fibre
Upper motor neuron: Cell bodies in primary motor area (pyramid cells) → most axons cross over
to opposite side in medulla and go down spinal cord
Lower motor neuron: Cell body ventral horn → ventral root into spinal nerve → peripheral nerve
(and often via a plexus) → muscle fibre
general structure of a nerve
Nerve is surrounded by epineurium, contains fascicles (within perineurium) which are made up of myelinated axons (encased in endoneurium). Nerves also contain blood vessels.
typical acending tract function
Sensory, i.e. pressure, touch, temperature, pain, etc. Afferent, i.e. transmitting stimuli from the periphery and internal organs to the CNS
typical acending tract number of neurons in the pathway
Three (first, second and third
order)
typical acending tract origin
Receptors (distal branch of
first order neuron, cell body in
dorsal root ganglion) on body
surface, muscles or in organs
typical acending tract termination
Primary sensory cortex, some
in cerebellum
typical acending tract where does it cross over (decussate)
Spinal level, i.e. same level
where first order neuron
enters the spinal cord
typical decending tract function
Motor, both skeletal and smooth muscle fibres Efferent, i.e. sending impulses from CNS to skeletal muscles, smooth muscles in organs and blood vessels
typical decending tract number of neurons in the pathway
Two (upper and lower)
typical decending tract origin
Primary motor cortex in precentral gyrus, basal nuclei and
cerebellum
typical decending tract termination
Neuromuscular junction or
synapses on smooth muscle
fibres
typical decending tract where does it cross over (dessucate)
In medulla, but some tracts
don’t cross over
typical decending tract examples of tracts
Pyramidal, extrapyramidal
DRAW DIAGRAM OF REFLEX ARC
DRAW DIAGRAM OF REFLEX ARC
Neuropathic pain could have several reasons. Explain a reason
A decreased threshold for action potential generation in pain neurons.
(If the threshold OF -55 is decreased, a weaker stimulus will generate an action potential and get
perceived as pain.)
Explain the phenomenon of referred pain.
Visceral nociceptor get triggered by painful stimuli in the internal organs. Often these stimuli are
due to insufficient blood supply to that organ, causing ischaemia. Their fibres are bundled
together with fibres from pain receptors of specific skin areas and travel the same pathways to
the same regions in the CNS where the pain is perceived. The brain can’t quite distinguish where
the stimulus came from – organ or skin so it is felt in both areas.
Example: Pain in the left arm and jaw during a myocardial infarction
- Which neurotransmitters and nerve fibres are involved in pain sensation?
Sharp pain – A fibres, burning and dull pain – C fibres
Neurotransmitters: Glutamate, substance P – they trigger second order neurons
These can be inhibited by the body’s own analgesia, i.e. endorphins and enkephalins
What is the difference between pain threshold and tolerance?
Threshold = the intensity of a stimulus that will be perceived as pain (not just pressure or
temperature). This is the same for every person
Tolerance = how pain is interpreted, perceived and tolerated. This varies from person to person and also
in different situations
Identify the 3 major roles of the ANS in relation to maintaining homeostasis
Cardiac regulation
• Secretory gland regulation (e.g. salivary, sweat, gastric, bronchial)
• Smooth muscle regulation (e.g. bronchi, blood vessels, GIT, urogenital)
There are no sympathetic neurons in the cervical spinal segments, yet there are three
cervical ganglia in the neck region. How can that be explained?
The preganglionic sympathetic fibers originate in the thoracic and lumbar segments of the spinal
cord. Some of these fibers ascend in the sympathetic trunk and synapse in three ganglia located
in the neck region (see figure 14.7)
Describe the meaning and importance of sympathetic and parasympathetic tone
“Tone” in the divisions of the ANS refers to the firing rate of sympathetic and parasympathetic
neurons. Sympathetic tone determines the degree of constriction or dilation throughout the
vascular system under resting conditions, while parasympathetic tone is important to determining
heart rate and GI function. The resting tone of each system aids in the maintenance of
homeostasis under normal conditions.
Sympathetic = vasomotor tone = slight vasoconstriction of arterioles during rest
Parasympathetic tone = vagus nerve keeps HR at 60-80
sympathetic NS origin
Thoraco-lumbar
Nerve cell bodies in lateral horns
T1-L2
sympathetic NS location of glangia
Alongside the spinal column –
sympathetic trunk ganglia
sympathetic NS length of pre and post ganglionic fibres
Short pre
Long post
sympathetic NS neurotransmitters and receptors
Preganglionic – ACh → nicotinic Postganglionic – NE → α, β Except to sweat glands – ACh → muscarinic Adrenal glands release adrenaline and noradrenaline → α, β
sympathetic NS functions
↑ mental alertness ↑ metabolism ↓ digestion & urine output ↑ respiration & dilate airways ↑ heart rate & blood pressure activate sweat glands control blood vessels
para sympathetic origin
Cranio-sacral
Cell bodies in some cranial nerve
nuclei, grey matter of S2-S4
para sympathetic location of ganglia
Close to or within the effector organs
para sympathetic length of pre and post ganglionic fibres
Long pre
Short post
para sympathetic neurotransmitters and receptors
Preganglionic – ACh → nicotinic
Postganglionic – ACh →
muscarinic
para sympathetic function
↓ metabolism ↑ salivary & digestive constrict airways ↓ heart rate & blood pressure ↑ gut motility & blood flow ↑ urine output & defecation
why might a person not have reflexes
Jimmy is in spinal shock. This is a transient period that follows the injury and can last for several
weeks. During spinal shock, there are no reflexes, flaccid paralysis below the affected level and
no sensation.
major nerves between c1 and 4
phrenic
major nerves between c5 and t1
brachial
axillary, musculocutaneous, median, radial, ulnar
major nerves between l1 and l4
femoral, obturator
major nerves between l4 and s4
sciartic (tibial and common fibular
