BMS1058 - The Nervous System Flashcards by Anya Anderson

The Resting Membrane potential of a typical neuon is around ____ mV. This is the same as the ______ potential difference.

This caused by uneven distribution of charged ions inside (__+) and outside (__+) of the neuronal membrane. What is this imbalance maintained by?

-70mV

Electrical potential difference.

inside = K+
outside = Na+

maintained by cell membrane permeability and the Na+/K+ pump.

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What is depolarisation?

When the inside of cell becomes more positive than outside.

Occurs when charge difference is more pos than RMP (-70mV).

↓ in potential difference across membrane = membrane less polarised

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What is repolarisation?

Membrane potential returns to its resting state after a change in charge towards a more –ve value (cell membrane more polarized).

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What is Hyperpolarisation?

When the charge continues past RMP and moves back to RMP (70mV)

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What are graded potentials?

Localised changes in membrane potential. This local event and depolsaisation does not spread along the neuron.

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What is an action potential?

Rapid & substantial neuron membrane depolarisation.

Membrane potential changes from RMP (70mV) to +30mV and back again.

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All action potentials begin as ______ _________. If these do not reach depolarization threhold nothing happens. If threshold reaches _______mV, AP will occur. This is known as the ‘__________’ principle.

Graded potentials.

15-20mV

‘All-or-none’ principle

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What is the absolute refractory period?

When the axon is in the process of generating an action potential and is unable to respond to another stimulus.

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What is the relative refraxctory period?

Once axon has dealt with a stimulus, it can deal with a new stimulus if it is of a greater magnitude than the
present one.

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What is a neuromuscular junction? What do the neurotransmitters bind to?

The synapse of a motor neuron to muscle fibres. Axon terminals protude to motor end plate.

Neurotransmitters bind to receptors on the plasmalemma.

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Why are APsonly transmitted in one direction.

Only presynaptic terminal has synaptic vesicles contianing neurotrasmitters, which are released into synaptic cleft.

Only the postsynpatic neuron has receptors for these neurotransmitters to bind to.

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What are the two types of neurons in the Periphery Nervous System?

Sensory (afferent) and Motor (efferent)

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What can the motor nerves be devided into?

Somatic (conscious) and Autonomic (subconscious)

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The area where sensory impulses terminate is called the ________ ________. What does this consist of?

Integration Centre.

Of decreasing movement complexity: Cerebral cortex, Thalamus, Cerebellum, Lower brian stem, Spinal cord.

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What are the 4 main regions of the brain?

Cerebrum
Diencephalon
Cerebellum
Brain Stem

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What does the Cerebrum consist of?

The brain consists of what 5 lobes? What are they in charge of?

Frontal Lobe: General Intellect & motor control

Temporal Lobe: Auditory input & interpretation

Parietal Lobe: General sensory input & interpretation

Occipital Lobe: Visual input & interpretation

Insular Lobe: Diverse functions linked to emotion & self-perception

What is the Diencephalon composed of? What do they do?

The Thalamus and Hypothalamus

Thalamus: relays all sensory input (except smell) to appropriate places.

Hypothalamus: maintains homeostasis - BP, HR, breathing, digestion etc

What does the Cerebellum do?

Coordinates timing of motor activities - pregression from one movement to the next.

Compares intended movement with actual changes in the body and initiates corrective adjustments.

What is the brain stem made up of? What specialised group of neurons does it house? What does it do?

Made up of the midbrain, pons and medulla oblongata.

Houses the reticular formation.

CV and respiratory function.
Skeletal muscles
Influences consciousness.
Circadian rhythm
Pain control

What is the autonomic system divided into?

Sympathetic, Parasympathetic and Enteric NS

What does the Enteric NS regulate? What can it function independent of?

GI function and motility

Can function indepently of CNS input, however doesn’t often do so

90% of vagal fribes between gut and brain are ______.

afferent (sending to the brain)

What are the 5 types of receptors in the sensory division of the PNS?

Mechanoreceptors
Thermoreceptors
Nociceptors
Photoreceptors
Chemoreceptors

What are the Sympathetic and Parasympathetic nervous systems responsible for?

Sympathetic - fight or flight Parasympathetic - Rest and Digest

How does the sympathetic NS affect the liver? Kidney?

Stimulates glucose release Causes vasoconstriction and decreases urine formation.

What neurons connect sensory and motor neurons?

Interneurons

What events would occur to pull your hand away from a hot surface?

Stimuli = heat, received by nociceptors and thermoreceptors Sensory APs travel to spinal cord. Integrated by interneurons. APs move to motor neurons and then to effectors. Muscles contract. Hand reflexivity moves without any thought (withdrawal reflex)

Name the 4 layers of the GI tract

Mucosa (inner) Submuscosa Muscularis Serosa (outer)

What are the 3 layers of the Muscosa in the GI tract?

Epithelial layer - simple columnar, cells secreting mucus, hormones etc Lamina propria - blood and lymph vessels - nutrient absorbtion Muscularis Mucosae - smooth muscle fibres

What is found in the Submucosa?

Connective tissue, blood and lymphatic vessels, neurons

The enteric NS is arranged in two _____. What are these called? Where are they located? What do they consist of?

Plexuses Myenteric plexus - in muscularis Submucosal plexus - in submucosa Plexuses consist of motor neurons, interneurons, and sensory neurons. (interneurons interconnect the neurons of the 2 plexuses).

_________ plexus mostly controls GI tract motility (frequency and strength of contractions) Motor neurons of ________ plexus control secretions of organs in GI tract.

Myenteric Submucosal

Where do sensory neurons sit in the enteric NS? What type of receptors do they have?

In the muscosal epithelium. Chemo (chemicals in food + pH) and mechanoreceptors (when food distends GI tract wall).

How does the ANS regulate the ENS?

Parasympathetic fibres of the vagus nerves and pelvic splanchnic nerves * Increase GI tract secretion and motility * Increase the activity of ENS neurons Sympathetic fibres from regions of the spinal cord * Decrease GI tract secretion and motility * Inhibit ENS neuron

What happens to the ENS in the gastric phase of digestion?

Food enters stomach Stretch receptors stimulated by gastric distension. Chemoreceptors activated if pH increases with protein. Nerve impulses to the submucosal plexus (secretions). Parasympathetic neurons activated. Output: Stomach - parietal cells secrete HCl and smooth muscle contracts (mixes and empties stomach) Negative feedback loop.

What happens to the ENS in the intestinal phase of digestion?

Distension of the duodenum by the presence of chyme. Stretch receptors in the duodenal wall signal to the medulla oblongata. Inhibit parasympathetic stimulation. Stimulate the sympathetic nerves to the stomach. OUTPUT: Gastric motility inhibited. Increase in contraction of the pyloric sphincter. Decreases gastric emptying.