Neuroanatomy Midterm Flashcards
how have neuroscientists learned about the brain?
observation of how damage or lesions to specific areas of the brain affect behavior and other neural functions
The nervous system is divided into what 2 systems?
- Central nervous system-brain and spinal cord
- Peripheral nervous system-all the neurons in the body outside the cns, cranial nerves, spinal nerves, ganglia-further divided into somatic nervous system and autonomic nervous system
Somatic Nervous System
part of the peripheral nervous system, made up of:
- afferent neurons- convey information from the sense organs to the brain and spinal cord
- efferent- carry motor instructions to the muscles from the brain
Autonomic Nervous System
part of the peripheral nervous system, made up of:
- sympathetic nervous system- a set of nerves that activate “fight or flight” response, preparing the body for action.
- parasympathetic nervous system- prepares the body to rest and conserve energy
how many miles of fibers are in the nervous system
90,000 miles
how many receptors do you have
19,000
What are glial cells?
They are the non excitable cells of the nervous system, they provide support and protection to the neurons.
- smaller than neurons
- capable of mitosis
- do not transmit impulses
- physically protect and help nourish neurons
- provide the supporting framework for all nervous tissue
- far outnumber neurons
what are the glial cells of the cns?
Astrocytes, ependymal cells, microglia and oligodendrocytes
what are astrocytes?
make up 90% of glial cells in cns -star like shape -help form the blood-brain barrier-strictly controls the substances entering the nervous tissue in the brain from the bloodstream. Fx: -regulate tissue fluid composition -provide structural integrity -replace damaged neurons -assist in new neuronal development
what are ependymal cells?
cuboid ET-cilia on apical surface circulate cerebral spinal fluid
line internal cavities
make contact with other glial cells
help form choroid plexus
what are microglia cells?
smallest % of CNS glial cells phagocytic -move through tissue in response to infection -remove debris -like macrophages
what are oligodendrocytes?
CNS glial cells
they are large with big body and processes
form myelin sheaths-speeds up transmission
what are the glial cells of the PNS?
satellite cells-flattened cells, cover somas in ganglia, separate soma from surrounding tissue fluid-regulate exchange
neurolemmocytes (schwann cells)-PNS myelination
What is myelination?
process by which part of an axon is wrapped with a myelin sheath
-forms a protective fatty coating
-glossy white appearance
The myelin sheath- supports, protects and insulates the axon
Where do voltage changes occur in myelination?
Voltage change occurs at the nodes, it cannot occur across the membrane in the insulated portion of an axon
oligodendrocyte- produce sheath in CNS
neurolemmocyte-produce sheath in PNS
difference between myelinated vs. unmyelinated
myelinated axon:
-nerve impulse “jumps from neurofibril node to neurofibril node (saltatory conduction)
-requires less ATP
-Produce faster nerve impulse
unmyelinated axon:
-must travel entire length of axon (continuous conduction)
-take longer to reach end of axon
-conduct nerve impulses from pain stimuli
Types of Nerves
- sensory (afferent)-convey sensory info to CNS
- motor (efferent)-convey motor impulses from CNS to muscles and glands
- mixed-both sensory and motor
what are the organs of the PNS?
nerves
Where do axons terminate?
as they contact other neurons, muscle cells or gland cells
where do axons transmit nerve impulses?
at a specialized junction with another neuron called synapse
Neuron Structure (Nerve Cell)
- cell body-nucleus–genetic info
- dendrites-recieve info
- axon-carry info long distances; myelin
- axon terminals-transmit info
Facts about Axons
- tip of a growing axon consists of a blob or protoplasm called a growth cone and is studded with chemical receptors
- these receptors sense the local environment
- causing the growth cone to be attracted or repelled by various cellular elements–thus pulled in a particular direction at each point along its path
Axon path finding process to develop synapses
The growth cone navigates through the brain until it reaches its destination area–here other chemical cues cause it to begin generating synapses
Many thousands of genes give rise to proteins that influence the axonal path finding. The pool of neurons is largely in place at birth–but still continues to develop for a long time afterward.
How large is a new born baby’s brain and how many nerve cells are present, after 40 weeks of gestation?
2/3 the size of an adult brain with one million million nerve cells (1,000,000,000,000)–however the intercellular connections which brain function depends on are far from complete
how many synapses does one mature cortical nerve cell have?
10,000 synapses per mature cortical nerve cell
average number of synapses in the individual’s cortex
10 to the 15th power
what can cause mental difficulties in childhood?
if the mother severely undernourished or in extreme mental stress during critical brain growth periods in gestation, also infections, drinking alcohol, taking drugs and smoking while she is pregnant is all transferred to the unborn child via the placenta
Average weight and consistency of the the brain
between 2.87 and 3.1 lbs, made of a very soft tissue that is jello-like. Pinkish on the outside and mostly white on the inside
Blood Brain Barrier
Blood vessels evert the CNS throughout the perivascular space above the pia mater, their cells in the vessel wall are bound tightly to form the bbb, to protect the brain from toxins that might enter through the blood stream. It is the separation between the circulating blood and extra cellular fluid in the CNS, occurring along all capillaries and consists of extra capillaries that don’t exist in normal circulation. Endothelial cells are in charge of restricting things like bacteria and hydrophilic molecules, while letting hydrophobic ones like O2, Hormones and CO2 diffuse through. They actively transport metabolic products (like glucose) across the barrier necessary for brain fx.
Telencephalon Region
aka Cerebrum–Cerebral Hemispheres that are separated by a deep midline sagittal fissure. In the depth of this fissure lies the corpus callosum with is the bridge between L & R hemispheres. A 2nd horizontal fold of the dura mater (tentorium cerebelli) separates these hemispheres from the cerebellum.
Corpus Callosum
“tough body” in latin
Wide body of neural fibers that connect the cerebral hemispheres
facilitates the inter-hemispheric communication
-largest white matter structure of the brain
200-250 axonal projections