49 Nervous System Flashcards
How many neutrons are there in the human brain?
Around 100 billion
What are the simplest animals with nervous system?
Cnidarians like Hydras and Jellies.
In what animals are distinct nervous systems seen?
Hydra, Sea stars, Planarians (flat worms), Leeches, Insects, Chitons (molluscs), Squid (molluscs) and Salamanders
What is the structure of the nervous systems of Hydras?
Interconnected nerve cells form a diffuse “nerve net” which controls the contraction and expansion of the gastrovascular cavity.
Unlike the nervous systems of other animals it lacks clusters of neurons that perform specialised tasks.
They also differ in the the ’nerve net’ is a net of individual axons, not nerves which are multiple axons bundled together.
What is the structure of the nervous systems of Sea stars?
They have a set of radial nerves connecting to a central nerve ring. Within each arm of a sea star, the radial nerve is linked to a nerve net from which it receives input and to which it sends signals controlling muscle contraction.
What is the structure of the nervous systems of Planarians (flatworms)?
They have a very small brain that leads to two longitudinal nerve cords that pass from the anterior (front) end to the posterior.
Along the length of these nerve cords they are connected by transverse nerves (the ‘rungs of a ladder’) to form a ladder-shpaed structure
What is the structure of the nervous systems of Leeches (annelids)?
They have a brain at the anterior end and a ‘ventral nerve cord’ that travels down to the posterior end.
Throughout the entire length of this ‘ventral nerve cord’ are ’segmental ganglia’ which act as processing centres along with the brain.
What is the structure of the nervous systems of Insects?
Like leeches they have a brain at the anterior end and a ‘ventral nerve cord’ that travels down to the posterior end.
Throughout the entire length of this ‘ventral nerve cord’ are ’segmental ganglia’ which act as processing centres along with the brain.
What is the structure of the nervous systems of Chitons (molluscs)?
They do not have a fully centralised brain but instead have a small ‘anterior nerve ring’ with many ganglia.
Nerve fibres extend from the nerve ring laterally. These are bridged by ‘longitudinal nerve cord.’
What is the structure of the nervous systems of Squid (molluscs)?
They have a highly advanced nervous system with an anterior brain and nerves that extend through the body. Some ganglia are seen on nerves out side the brain.
What is the structure of the nervous systems of Salamanders?
They have a brain that leads to a spinal cord (also called the dorsal nerve cord)
Along this spinal cord are sensory ganglia.
What are ‘ganglia’s?
A concentration of grey matter in the PNS that act as processing centres. (Basal ganglia are not true ganglia as they are in the CNS)
What do nerves do?
They channel and organize information that flows along specific routes through the nervous system.
What is a pattern seen in the nervous systems of bilaterally symmetrical organisms?
They exhibit ‘cephalisation’ which is an evolutionary trend towards a clustering of sensory neutrons and interneurons at the anterior (front) of the organism.
Chitons and squid are both molluscs but have vastly different nervous systems. What explains this?
Chitons are slow and sessile so have simpler nervous systems than predatory molluscs like squid and octopus which also have advanced eyes.
How do the nervous systems of vertebrates differ from that of invertebrates?
Vertebrates have spinal cords not nerve cords.
Vertebrates also differ in that they have distinct CNS and PNS.
What does “nuclei’ refer to with regard to the nervous system?
A group of neuron like a ganglia but that are in the CNS (ganglia are by definition PNS)
What is the purpose of the spinal cord?
To carry signals to and from the brain and to initiate reflexes.
What is an example of a reflex?
The knee jerk reaction.
How does the nerve cord’s location differ between vertebrate and invertebrates?
In vertebrates it is located dorsally (on the back) whereas in many invertebrates it is located ventrally (on the front) for protection when crawling.
What happens during the ‘knee-jerk reaction’?
The reflex is initiated artificially by tapping the tendon connected to the
quadriceps muscle. Mechanoreceptors detect a sudden stretch in the quadriceps, This signal is conveyed by sensory neurons to the spinal cord
In response to signals from the sensory neurons, motor neurons in the spinal cord convey signals to the quadriceps, causing it to contract and jerking the lower leg forward.
Sensory neurons also communicate with interneurons in the spinal cord. The interneurons inhibit motor neurons that lead to the hamstring muscle. This inhibition prevents contraction of the hamstring, which would resist the action of the quadriceps.
Where is the knee-jerk reaction seen naturally?
When someone is carrying a large load. If their knees begin to buckle the knee-jerk reaction holds the knees in place.
What is the basic structure of the brain?
It has a folded outer layer called the cortex that consists of grey matter.
On the inside of the brain is white matter.
At the very centre of the brain is are ventricles that are filled by cerebrospinal fluid.
What does the central nervous system develop from?
The ‘hollow dorsal nerve cord’
What happens to the hollow interior of the ‘hollow dorsal nerve cord’ when the embryo develops?
It becomes the ventricles and the “central canal” of the spinal cord.
Both of these are filled with cerebrospinal fluid.
How is cerebrospinal fluid produced?
By the brain which forms it by filtering blood from the arteries.
What happens to cerebrospinal fluid once it is in the brain?
It circulates through the central canal of the spinal cord and the brain’s ventricles before draining into veins.
What is the importance of the cerebrospinal fluid?
It supplies the brain with nutrients and hormones and carries away wastes.
In mammals, the cerebrospinal fluid also cushions the brain and spinal cord by circulating between layers of connective tissue that surround the CNS.
What surrounds the ventricles of the brain and what is its function?
Ependymal cells that have cilia too promote the circulation of cerebrospinal fluid.
What are some specific types of glial cells?
Oligodendrocytes, Schwann cells, microglia, astrocytes and radial glia
What are microglia?
Glial cells that are actually immune cells who protect the brain from pathogens.
What are astrocytes?
Glial cells that facilitate information transfer at synapses and in some instances release neurotransmitters.
Astrocytes next to active neurons cause nearby blood vessels to dilate, increasing blood flow and enabling the neurons to obtain oxygen and glucose more quickly.
Astrocytes also regulate extracellular concentrations of ions and neurotransmitters.
What are radial glia?
Glial cells found in embryos. They form tracks along which newly formed neurons migrate from the neural tube, the structure that gives rise to the CNS
How can neurons be regenerated?
By radial glia and astrocytes which can act as stem cells to generate new neurons and glia.
Astrocytes facilitate information transfer, dilate blood vessels and regulate the extracellular environment.
What other function do they have?
Astrocytes induce cells that line the capillaries to form tight junctions. This regulates what substances can leave the capillary as it passes through the brain.
This is called the ‘blood-brain barrier’ and helps prevent pathogens from entering the brain.
What is the spinal cord divided into?
From anterior to posterior:
Cervical, Thoracic, Lumbar, Sacral
What do afferent neurons do?
Carry signals to the brain
What do efferent neurons do?
Carry signals away from the brain.
What do afferent neurons carry signals from?
Sensory receptors
What system do efferent neurons lead to?
The motor system and the autonomic system
What does the motor system do?
Controls skeletal muscles.
What does the autonomic system do?
Controls involuntary actions. such as smooth muscles, cardiac muscle, glands and organs
What is the autonomic system divided into?
The sympathetic division, the parasympathetic division and the enteric division.
What is the fundamental purpose of the sympathetic division?
To mobilise energy resources, increase circulation and otherwise increase the body’s ability to ‘fight of flight’
What is the fundamental purpose of the parasympathetic division?
To counter the sympathetic division and thus conserve the body’s resources.
What are the specific responses to activation of the parasympathetic division?
Constricts pupil of eye
Stimulates salivary gland secretion
Constricts bronchi in lungs (reduces airflow)
Slows heart
Stimulates activity of the stomach and intestines
Stimulates activity of the pancreas
Stimulates gallbladder
Promotes emptying of the bladder
Promotes erection of the genitalia]
(total: 9)
What are the specific responses to activation of the sympathetic division?
Dilates pupil of eye
Inhibits salivary gland secretion
Relaxes bronchi in lungs causing them to dilate and thus increasing air flow.

Accelerates heart
Inhibits activity of stomach and intestines

Inhibits activity of pancreas

Stimulates glucose release from liver; inhibits gallbladder
Stimulates adrenal medulla to secrete epinephrine and norepinephrine.

Inhibits emptying of bladder

Promotes ejaculation and vaginal contractions
What is the enteric division of the nervous system?
The division which regulates the digestive system i.e peristalsis.
The enteric division is also regulates by the sympathetic and parasympathetic systems but can function on its owns.
When the brain first forms what does it consist of?
A forebrain, mid brain and hind brain.
In an embryo at 5 weeks, what has the forebrain become?
A ’telencephalon’ and a ‘diencephalon’
In an embryo at 5 weeks, what has the midbrain become?
The ‘mesencephalon’
In an embryo at 5 weeks, what has the hindbrain become?
The ‘metencephalon’ and the ‘mylencephalon’
What does the telencephalon become?
The cerebrum (includes cerebral cortex, white matter, basal nuclei)
What does the diencephalon become?
It becomes a developed diencephalon which includes the thalamus, hypothalamus and epithalamus
What does the mesencephalon become?
The midbrain (part of brainstem)
What does the metencephalon become?
The pons (part of brainstem) and the cerebellum
What does the myelencephalon become?
The medulla oblongata (part of brain stem)
What does the Cerebrum arise from?
The telencephalon from the forebrain
What does the Diencephalon arise from?
The diencephalon from the forebrain
What does the Midbrain arise from?
The mesencephalon from the midbrain
What does the Pons arise from?
The metencephalon from the hind brain
What does the Cerebellum arise from?
The metencephalon from the hind brain
What does the Medulla oblongata arise from?
The myelencephalon from the hind brain
Ultimately what does the forebrain develop into?
The cerebrum and the Diencephalon
Ultimately what does the midbrain develop into?
The midbrain
Ultimately what does the hindbrain develop into?
The pons, cerebellum and medulla oblongata
What does the cerebrum include?
The cerebral cortex, white matter, basal nuclei and the corpus callosum
What are basal ganglia also known as?
Basal nuclei.
What are basal nuclei also known as?
Basal ganglia.
What does the diencephalon include?
The thalamus, hypothalamus, epithalamus, pineal gland and pituitary gland.
What does the brain stem include?
The midbrain, pons and medulla oblongata.
What are the basic regions of the brain?
Cerebrum, cerebellum, diencephalon and the brain stem.
What is the structure of the thalamus?
It is two walnut sized masses joined together.
What is the function of the thalamus?
It is the main input center for sensory information going to the cerebrum.
Incoming information from all the senses is sorted in the thalamus and sent to the appropriate cerebral centers for further processing.
What is the function of the hypothalamus?
It contains the body’s thermostat aswell as the central biological clock.
By controlling the pituitary gland it regulates hunger and thirst, plays a role in sexual and mating behaviours, and controls the fight-or-flightresponse.
The hypothalamus is also the source of posterior pituitary hormones and of releasing hormones act on the anterior pituitary
In what region of the brain is the thalamus?
Diencephalon
In what region of the brain is the hypothalamus?
Diencephalon
In what region of the brain is the pineal gland?
Part of the epithalamus which is in the Diencephalon
In what region of the brain is the epithalamus?
Diencephalon
In what region of the brain is the midbrain?
The brainstem
In what region of the brain is the pons?
The brainstem
In what region of the brain is the medulla oblongata?
The brainstem
What is the ‘epithalamus’
A region of the brain which contains the pineal gland and several clusters of capillaries that generate cerebrospinal fluid from blood.
What is the brain stem divided into?
The midbrain, pons and ‘medulla oblongata’
What is the function of the ‘midbrain’
it receives and integrates sensory information and sends it to specific regions of the forebrain. For example all sensory axons involved in hearing pass through it.
It also mediates visual reflexes such as the ‘peripheral vision reflex’ in which the head turns to objects it sees in tis peripheral vision.
What is the ‘peripheral vision reflex’?
The reflex in which the head turns to face objects that it sees in the peripheral vision.
This reflex is mediated by the ‘midbrain’ which is part of the brainstem.
What are the functions of the pons?
Along with the medulla oblongata, it helps transfer information from the PNS to the midbrain and forebrain. They also help co-ordinate large scale movements i.e. running.
It also regulates the breathing centres of the medulla oblongata.
Where in the brain is breathing controlled?
Medulla oblongata
Where in the brain is heart activity controlled?
Medulla oblongata
Where in the brain is temperature controlled?
Hypothalamus
Where in the brain is CO2 levels in the blood controlled?
Medulla oblongata (it regulates these by affecting the rate of breathing)
What are the functions of the medulla oblongata?
Along with the pons, it helps transfer information from the PNS to the midbrain and forebrain. They also help co-ordinate large scale movements i.e. running.
It also plays a major role in the autonomic and homeostatic systems by controlling breathing, heart and blood vessel activity, swallowing, vomiting, and digestion.
What is the cerebellum involved in?
It coordinates movement and balance and helps in learning and remembering motor skills.
How does the cerebellum co-ordinate muscle movement?
It integrates sensory information from the muscles to determine their length and from the joints to determine their orientation.
It also takes visual and auditory information (vestibular system - balance) and also monitors signals sent by the cerebrum
What is the general purpose of the cerebrum?
It is involved in learning, emotion, memory and perception.
What is the structure of the cerebrum?
It consists of two hemispheres, each joined by a ‘corpus callosum’
Each hemispheres has a cerebral cortex and basal nuclei
What is the ‘corpus callosum’?
The fibrous tract which joins the two hemispheres and thus allow site co-ordination of actions.
How are the hemispheres of the brain labelled?
When viewed form the from the left hemisphere appears on the right and vice versa.
What do the basal nuclei do?
They serve as centers for planning and learning movement sequences.
What are the basic functions handled by the brain outside the cerebral cortex?
‘Arousal and sleep’, ‘biological clock regulation’ and ‘emotions’
How can the level of sleep be quantified?
With an EEG
What does ’EEG’ refer to?
Electroencephalogram
What does an EEG do?
It measures the electrical signals of the brain.
How are the electrical signals of the brain monitored?
With an EEG (electroencephalogram)
How would an EEG indicate wakefulness?
High frequency waves with low amplitudes indicate wakefulness.
During sleep the waves decrease in frequency with each having a larger amplitude.
Would large brainwaves i..e /\/\/\/\/\ indicate wakefulness or sleep?
Sleep.
Where is sleep/wakefulness regulated?
In the ‘reticular formation’
What is the ‘reticular formation’ involved in?
The regulation of sleep/wakefullness
Where is the ‘reticular formation’?
It is a diffuse network of neurons in the core of the brainstem.
How does the ‘reticular formation’ regulate sleep/wakefulness?
It acts as a sensory filter and thus receives signals from the eyes, ears and touch receptors etc.
It selectively relays these signals to the
What structures of the brain are involved principally in sleep/wakefulness?
The ‘reticular formation’ acts as the control centre.
If it activates the pons and the medulla oblongata this leads to sleepiness
Activation of the midbrain leads to arousal.
How is sleep regulated once the stimuli have been processed in the ‘reticular formation’, pons and medulla?
Melatonin production peaks at the night, leading to a sense of sleepiness.
What chemical regulates sleepiness?
Melatonin - at high levels it leads to sleep
What does Melatonin regulate?
Sleepiness - at high level it promotes sleeping.
How is the circadian rhythm maintained?
The timing is regulates by the ‘biological clock’
This is fine tuned based on visual etc. input
What does ‘circadian rhythm’ refer to?
Technically only the temporal pattern of activity.
The actual time keeping is done by the ‘biological clock’
What does ’biological clock’ refer to?
The molecular mechanism that directs periodic gene expression and cellular activity.
It therefore allows the body to know what time it is/
What are the molecular mechanism that allow the body to determine the time called?
The ‘biological clock’
If kept without sensory input, what period would the human biological clock have?
24.2 hours.
Where is the biological clock performed?
In the ’suprachiasmatic nucleus’ (SCN)
What does ’SCN’ refer to?
The ’suprachiasmatic nucleus’
What does ’suprachiasmatic nucleus’ refer to?
The cluster of neurons in the hypothalamus which
Where are the adrenal glands located?
Near the KIDNEYS
Where is the thymus located?
Behind the HEART
Where the the suprachiasmatic nucleus located?
In the hypothalamus
What are the parts of the brain which regulate emotion collectively called?
The ‘limbic system’
What are the parts of the brain which regulate emotion collectively called?
The ‘limbic system’
What does the ’limbic system’ refer to?
The parts of the brain which regulate emotion.
This includes the ‘amygdala’, ’nucleus accumbens’, hippocampus and thalamus
What does the ’limbic system’ refer to?
The parts of the brain which regulate emotion.
This includes the ‘amygdala’, ’nucleus accumbens’, hippocampus and thalamus
What does the ‘limbic system’ do?
It is primarily involved in regulating emotion.
However it is also involved in motivation, olfaction, behaviour and memory
What does the ‘limbic system’ do?
It is primarily involved in regulating emotion.
However it is also involved in motivation, olfaction, behaviour and memory
What is the amygdala?
An almond-shaped mass of nuclei (clusters of neurons) located at base of the cerebrum.
What is the amygdala?
An almond-shaped mass of nuclei (clusters of neurons) located at base of the cerebrum.
What is the role of the amygdala?
It is is strongly associated with sad etc. emotions and is involved strongly in ‘emotional memory’
What is the role of the amygdala?
It is is strongly associated with sad etc. emotions and is involved strongly in ‘emotional memory’
What is the ’nucleus accumbens’?
A brain structure which is primarily involved in the perception of pleasure.
What is the ’nucleus accumbens’?
A brain structure which is primarily involved in the perception of pleasure.
How does the amygdala differ from the ’nucleus accumbens’?
The amygdala is primarily involved in emotional memory and thus is activated strongly during sad music.
The ’nucleus accumbens’ is strongly involved in the perception of pleasure and thus is activated by happy music?
How does the amygdala differ from the ’nucleus accumbens’?
The amygdala is primarily involved in emotional memory and thus is activated strongly during sad music.
The ’nucleus accumbens’ is strongly involved in the perception of pleasure and thus is activated by happy music?
What region of the brain will happy music activate? (amygdala or nucleus accumbens)
The nucleus accumbens
What region of the brain will happy music activate? (amygdala or nucleus accumbens)
The nucleus accumbens
What region of the brain will sad music activate? (amygdala or nucleus accumbens)
The amygdala
What region of the brain will sad music activate? (amygdala or nucleus accumbens)
The amygdala
What is the general part of the brain in which speech and language are processed?
The frontal lobe of the cerebrum.
Where in the brain is language processed?
Primarily in ‘Wernicke’s area’
Where in the brain is the formation of speech performed?
In ‘Broca’s area’.
What would happened to a patient without Brocas area?
There would not be able to speak, but would comprehend language.
What would happen to a patient Wernickes area?
They would not be able to comprehend language.
If a person was not able to comprehend language, what area of the brain in likely malfunctioning?
The ‘Wernicke’s area’
If a person was not able to speak, what area of the brain in likely malfunctioning?
Broca’s area
How is ‘Broca’s’ area involved in speech?
It regulates the muscle of the face.
What areas of the brain would hearing words activate?
The auditory cortex and Wernickes area
What areas of the brain would seeing words activate?
The ‘visual cortex’ and ‘visual association cortex’
What areas of the brain would speaking words activate?
The ‘motor cortex’ and ‘Broca’s area’
What areas of the brain would generating words activate?
The prefrontal cortex (decide which words to use) and ‘Broca’s’ area
What are the lobes of the brain?
The ‘fontal lobe’, ‘parietal lobe’, ‘occipital lobe’ and ’temporal lobe’
