Hubs 2 Flashcards
Describe the general functions of the nervous system
Sensory: monitor/receives information about the external and internal environments and communicates this information to integrative areas.
Integration: processing, distribution and interpretation of input signals and processing and distribution of output signals to initiate body responses/ activities
Motor: Activation of effector organs/cells (muscles and glands) to cause an appropriate action/response in relation to existing sensory information
outline division one of the nervous system
Receptors- are sensory structures that detect changes in the internal and external environment
(Stomatic sensory receptors provide position, touch, pressure, touch, pressure, pain the temperature sensation)
(special sensors receptors provide sensations of smell, taste, vision, balance and hearing)
outline division two of the nervous system
The sensory division of the PNS brings information to the CNS from receptors in peripheral tissue and organs
Outline division three of the nervous system
information proceeding includes the integration and distribution of information in the CNS
Outline division four of the nervous system
The motor division of the PNS carries motor commands from the CNS to peripheral tissue
includes:
The somatic nervous system: skeletal muscles The Atomic nervous (ANS): - smooth - cardiac - glands -Adipose tissue
describe multipolar neurons
Have two or more dendrites and a single axon. Most common nueron type in the nervous system
describe unipolar neurons
Dendrites are continuous with the axon and the axon and cell body lies off to one side of axon. Most sensory nuerons are unipolar neurons
describe anaxonic neurons
All cell processes look alike ( no distinct axon). Located in the brain and some special sense organs but functions are poorly understood.
describe bipolar neurons
Have two distinct process- single dendrite with distal branches and a single axon. Rare, found only in some special sense organs
List the general function of Astrocytes (CNS) of neuroglia (5)
The most abundant neurogilia of theCNS, these cells:
- provide structural and metabolic support for neurons (e.g. mediate nutrients) exchange between neurons and blood vessels.
- Regulate ion, nutrients and gas concentrations in the extracellular fluid (ECF)
- Maintain the blood-brain barrier (BBB)
- Modulate synaptic transmission
- Form scar tissue after CNS injury
Describe the general function of Ependymal cells (CNS) of neuroglia
From an epithelium called the ependyma which fluid-filled spaces in the brain and spinal cord. These cells produce, monitor and circulate cerebrospinal fluid (CSF) through these spaces and also around the brain and spinal cord
Describe the general function of Microglia (CNS) of neuroglia
Related to monocytes/macrophages, these cells are mobile through nervous tissue and removing cellular debris, waste products and pathogens by phagocytosis
Describe the general function of Oligondroctyes (CNS) of neuroglia
These cells provide structural framework by stabilizing the position of neuronal axons and they produce myelin which wraps axons in myelin sheaths
Describe the general function of Schwann cells (PNS) of neuroglia
Schwann cells form a sheath around segments of peripheral neurons. This isolates the neurons from contact with the ECF. In most cases, the schwann cells from multi-layered myelin sheaths around a segment of the axon, just like obligodendrocytes in the CNS.
differentiate between white and gray matter
Axons that are surrounded by myelin sheaths are said to be myelinated (they have tiny gaps in between myelin sheaths are called nodes). Due to the lipids in myelin sheaths, myelinated axons appear white upon dissection, so regions that are dominated by myelinated axons make up the white matter of the nervous system, while areas that contain unmyelinated axons, cell bodies and dendrites make up the gray matter.
describe resting membrane potential (RMP) (3)
- When a neuron is neither receiving nor sending impulses it is considered to be resting. In this state, the cell is charged, but there is no change in voltage (e.g. no movement of ions across membrane)
- The change of a resting neuron is negative inside the cell compared to outside the cell; this gives the cell membrane a negative resting potential. The value of the RMP is genrally around -70mv (range: -50mv to -90mv)
- changes in a neurons’ RMP are the communication signals may be positive or negative relative to the RMP
Describe depolarization
During depolarisation the voltage change is positive (cell membrane becomes more positively charged). In other words, the RMP moves towards 0mv. Depolarisation is caused by excitatory stimuli and can lead to the generation of action potentials
Describe hyperpolarization
During hyperpolarization, the voltage change is negative (cell membrane becomes more negatively charged) and the RMP moves further away from 0mv. Hyperpolarization is caused by inhibitory stimuli as it cannot lead to an action potential.
describe graded membrane potentials
Graded membrane potentials are changes in the voltage are changes in the voltage of the neurons cell membrane (changes in value of the RMP). They are caused by stimuli received within the receptive region of ion membrane channels, allowing ions in and/or out of the cell.
Describe the excitatory post-synaptic potential (EPSPs) in relation to graded membrane potentials
These are graded potentials caused by excitatory stimuli which lead to depolarization
Describe the inhibitory post-synaptic potentials (IPSPs) in relation to graded membrane potentials
these are graded potentials caused by inhibitory stimuli lead to hyperolarization
describe summation
Summation refers to the TOTAL change of voltage within the entire receptive region of a neuron within a certain period of time. Summation determines whether or not a neurons will fire an action potentials, as a particular voltage value must be met for an action potentials to fire. This particular volatge value is known as the the threshold value.
Describe Action potential
AN action potential is the change in voltage of teh cell membrane taht occurs due to the opening and closing of ion channels progressively down the axon.
describe ion channel inactivation (4)
- An AP is conducted down the length of the axon in only one direction- towards the axon terminals.
- This is achieved by the inactivation of the Na+ channels after they close at the end of depolarization.
- Inactive Na+ channels cannot be stimulated to re-open immediately.
- Thus, while a particular segment of axon is depolariozed, stimulating the voltage-gated ion channels in the adjucent segments, only the axonal segment towards the axon terminals can open their ion channels; therefore the action potential continues in the same direction.
describe refractory periods (2)
- Absolute refractory period: While Na+ channels on axon segment are open, the neuron cannot respond to any incoming stimuli (i.e. is incapable of generating a new ATP)
- Relative refractory period: When the Na+ channels on an axon segment become inactive it causes a brief increase in the neurons threshold value. During this period only very strong stimuli can cause the generation of new AP.
Describe AP velocity (2)
- Axon diameter: the wider the axon diameter, the faster the AP travels. This is because there is less resistance to the flow of the local currents due to the increased space.
- Myelination: the presence and amount of myelin on axon also increases the speed of APs. As myelin sheaths wrap only segments of axon, they leave gaps of exposed axon called nodes of Ranvier.
It is at there nodes that the movement of ions can take place (not across the areas of membrane covered by myelin sheaths). Therefore the AP ‘skips’ from node to mode, getting to the axon terminals more quickly. This type of AP conduction is known as saltatory conduction.
describe the two different synapse
- Electrical synapses are rare, found only in certain areas of the nervous system.
- chemical synapses make up the vast majority of synapses in the body.
Define Neurotransmitters
Neurotransmitter are chemicals produced and released by neurons to stimulate, or inhibit, particular actions in the postynaptic cells.
describe 9 neurotransmitters
- Histamine
- Endorphins
- Norepinephrine (NE)/ Noradrenaline
- Nitric oxide (NO)
- Acetylcholine
- Dopamine
- Epinephrine/ adrenaline
- GABA
- Seration
