Chapter 4 - Anatomy Of The nervous System Flashcards
What is the central nervous system (CNS)?
The brain and the spinal cord
What is the peripheral nervous system (PNS)?
Connects the brain and spinal cord to the rest of the body.
What is the somatic nervous system?
It is part of the PNS. It consists of axons conveying messages from the sense organs to the CNS and from the CNS to the muscles. The axons to the muscles are an extension from cell bodies in the spinal cord, so part of each cell is in the CNS and part in the PNS.
What is the autonomic nervous system?
It is part of the PNS. It controls the heart, intestines, and other organs. This system has some of its cell bodies within the brain or spinal cord and some in clusters along the sides of the spinal cord.
What is dorsal?
The top of the brain for a 4 legged animal. For humans it is towards the back.
What is ventral?
In a 4 legged animal it is the bottom of the brain but in a human it is towards the stomach
What is anterior?
Toward the front end
What is posterior?
Toward the rear
What is superior?
Above another part
What is inferior?
Below another part
What is lateral?
Towards the side, away from the midline
What is medial?
Toward the midline, away from the side
What is proximal?
Located close to the point of origin or attachment
What is distal?
Located more distant from the point of origin or attachment
What is ipsilateral?
On the same side of the body
What is contralateral?
On the opposite side of the body
What are the 3 main ways in which to cut the brain?
Coronal plane (frontal plane, brain structures as seen of the front), Sagittarius plane (brain structures as seen from the side), horizontal plane (transverse plane, brain structures as seen from above)
What is a fissure?
A long, deep sulcus.
What is sulcus?
A fold or groove that separates one gurus from another
What is a gyrus?
a protuberance on the surface of the brain
What is a ganglion?
A cluster of neuron cell bodies, usually outside the CNS
What is a nucleus?
A cluster of neuron cell bodies within the CNS
What is a nerve?
A set of axons in the periphery, either from the CNS to a muscle or gland or from a sensory organ to the CNS
What is a tract ?
A set of axons within the CNS, also known as a projection.
What is a column?
A set of cells perpendicular to the surface of the cortex, with similar properties. eg. if one cell in column responds to touch on the palm of the left hand then the other cells in that column do too.
What is a lamina?
A row or layer of cell bodies separated from other cell bodies by a layer of axons and dendrites. The brain has 6 distinct laminae. The laminae are layers of cell bodies that are parallel to the surface of the cortex ad separated from each other by layers of fibers.
The laminae vary in thickness and prominence from one part of the cortex to another and a given lamina may be absent rom certain areas.
eg. Lamina 4 receives axons from the various sensory nuclei of the thalamus is prominent in all the primary sensory areas but absent from the motor cortex.
What is the spinal cord?
part of the CNS, within the spinal column. The spinal cord communicates with all sense organs and muscles except those of the head. It is a segmented structure and each segment has on each side a sensory nerve and a motor nerve.
What is the Bell-Magendie law?
the entering dorsal roots (axon bundles) carry sensory information and the exiting ventral roots carry motor information. The axons to and from the skin and the muscles are the peripheral nervous system. Note the cell bodies of the motor neurons are inside the spinal cord.
what is a dorsal root ganglia?
The cell bodies of the sensory neurons are in clusters of neurons outside the spinal cord.
What is inside the spinal cord?
There s an H shape which consists of the grey matter. Densely packed with cell bodies and dendrites. Many neurons of the spinal cord send axons from the gray matter to the brain or other parts of the spinal cord through the white matter,which consist of myelinated axons.
Why are the segments of the spinal cord important?
each segment sends sensory info to the brain and receives motor commands from the brain. All the information passes through tracts of axons in the spinal cord. if the spinal cord is cut at a given segment, the brain loses sensation from that segment and below. The brain loses moor control over all parts of the body serves by that segment ad the lower ones.
What is the autonomic nervous system?
It consists of neurons that receive info from and send commands to the heart, intestines and other organs. It has 2 parts, the sympathetic and the parasympathetic nervous systems
What is the sympathetic nervous system responsible for?
The sympathetic nervous system is a network of nerves that prepare the organs for vigorous activity, consists of chains of ganglia just to the left and right o the spinal cord’s central regions (the thoracic and lumbar areas). These ganglia are connected by axons to the spinal cord. Sympathetic axons prepare the organs for fight or flight (increasing breathing, heart rate and decreasing digestive activity). Because the sympathetic ganglia are closely linked, they often act as a single system in sympathy with one another.
What receives only sympathetic input?
The sweat glands, the adrenal glands, the muscles that constrict blood vessels, and the muscles that erect the hairs of the skin.
What does the parasympathetic nervous system do?
It facilitates vegetative nonemergency responses. They are generally the opposite to the sympathetic responses. Generally both the parasympathetic and the sympathetic nervous systems are both active to varying degrees and many stimuli arouse parts of both systems.
Why is the parasympathetic nervous system also known as the craniosacral system?
Because it consists of the cranial nerves and nerves from the sacral spinal cord.
Describe the ganglia of the parasympathetic nervous system.
Unlike the ganglia in the sympathetic system, the parasympathetic ganglia are not arranged in a chain near the spinal cord. Rather long preganglionic axons extend from the spinal cord to parasympathetic ganglia close to each internal organ. Shorter postganglionic fibers then extend from the parasympathetic gsnglia into the organs. Because parasympathetic ganglia are not linked to one another,they act more independently. It works to conserve energy.
What neurotransmitters do the parasympathetic and sympathetic nervous systems use?
The parasympathetic nervous systems’ postganglionic axons release acetylcholine. Most of the postganglionic synapses of the sympathetic nervous system use norepinephrine, although a few, like those that control the sweat glands use acetylcholine. Because the two systems use different neurotransmitters, certain drugs excite one system or the other.
Name the 6 segments of the spinal cord.
Cranial nerves (12 pairs), cervical nerves (8 pairs), thoracic nerves (12 pairs), lumbar nerves (5 pairs), sacral nerves (5 pairs), coccygeal nerves (1 pair).
What is the hindbrain?
The posterior part of the brain consisting of the medulla, the pons, and the cerebellum. These are all part of the brain stem.
What is the brain stem?
the medulla, the pons, the cerebellum and certain central structures of the forebrain (thalamus, superior colliculus, inferior colliculus, tectum, tegmentum, pineal gland)
describe the medulla oblongata.
it is just above the spinal cord and can be regarded as an enlarged extension of the spinal cord into the brain. It controls vital reflexes (breathing, heart rate, vomiting, salivation, coughing, and sneezing) through the cranial nerves. Damage to the medulla is often fatal and large doses of opiates are life threatening because they suppress activity of the medulla.
Describe the cranial nerves.
The cranial nerves control sensations from the head, muscle movements in the head, and much of the parasympathetic output to the organs. Some of the cranial nerves include both sensory and motor components, whereas others have just one or the other.
Just as the lower parts of the body are connected to the spinal cord via sensory and motor nerves, the receptors and muscles of the head and organs connect to the brain by 12 pairs of cranial nerves (one of each pair on the right side and one on the left). Each cranial nerve originates in a nucleus (cluster of neurons) that integrates the sensory information, regulates the motor output or both. The cranial nerves run through the forebrain, midbrain and hindbrain.
Describe the pons.
The pons lies anterior and ventral to the medulla. In the pons, axons from each half of the brain cross to the opposite side of the spinal crd so that the left hemisphere controls the muscles of the right side of the body and visa versa. The medulla and the pons contain the reticular formation and the raphe system that control the motor areas of the spinal cord. The ascending portion sends output to much of the cerebral cortex, selectively increasing arousal and attention in one area or another.
What is the raphe system?
It sends axons to much of the forebrain, modifying the brain’s readiness to respond to stimuli
Describe the cerebellum
This is the large hindbrain structure. It controls movement, balance and coordination, help with shifting focus (between auditory and visual stimuli), and timing (people with damage here are poor at judging which rhythm is faster).
Describe the midbrain.
The roof of the midbrain is called the tectum. The swellings on either side of the tectum are the superior colliculus and the inferior colliculus. Both are important for sensory processing. The inferior colliculus for hearing and the superior colliculus for vision.
Under the tectum lies the tegmentum. This includes the 3rd and 4th cranial nerves, parts of the reticular formation, and extensions of the pathways between the forebrain and the spinal cord or hindbrain. Another structure is the substantia nigra which gives rise to a dopamine-containing pathway that facilitates readiness fr movement
Describe the forebrain
It has 2 cerebral hemispheres. Each hemisphere is organised to receive sensory information (mostly from the contralateral side of the body) and to control muscles (mostly on the contralateral side) by way of axons to the spinal cord and the cranial nerve nuclei.
The outer portion is the cerebral cortex. Under this is the thalamus (which is the main source of information to the cerebral cortex). The basal ganglia are a set of structures important for certain aspects of movement. A number of other interlinked structures, known as the limbic system, form a border around the brainstem. These structures are particularly important for motivations and emotions such as eating, drinking sexual activity, anxiety and aggression. The limbic system includes the olfactory bulb, hypothalamus, hippocampus, amygdala, and cingulate gyrus of the cerebral cortex.
Describe the thalamus.
It is a pair of structures (one in the left hemisphere, one in the right). It resembles 2 avocados joined. Most sensory information goes first to the thalamus, which processes it and sends output to the cerebra cortex. An exception to this rule is olfactory information, which progresses from the olfactory receptors to the olfactory bulbs and then directly to the cerebral cortex.
Many nuclei of the thalamus receive their input from a sensory system and transit information to a single area in the cerebral cortex. The cerebral cortex sends information back to the thalamus, prolonging and magnifying certain kinds of input at the expense of others, thereby focusing attention on particular stimuli
What are the parts of the limbic system?
Cingulate gyrus, thalamus, hypothalamus, mamillary body, hippocampus, amygdala, olfactory bulb
Describe the hypothalamus
a small area near the base of the brain just ventral to the thalamus. It has widespread connections with the rest of the forebrain ad the midbrain. Partly through nerves and partly through hypothalamic hormones, the hypothalamus conveys messages to the pituitary gland.altering the release of hormones. Damage to any hypothalamic nucleus leads to abnormalities in motivated behaviours such as feeding, drinking, temperature regulation, seual behaviour, fighting, or activity level.
What is the pituitary gland?
The pituitary gland is an endocrine (hormone producing) gland attached to the base of the hypothalamus by a stalk that contains neurons, blood vessels and connective tissue. In response to messages from the hypothalamus, the pituitary synthesises hormones that the blood carries to organs throughout the body.
Describe the basal ganglia.
The basal ganglia is a group of subcortical structures lateral to the thalamus. It includes the caudate nucleus, the putamen, and the globus pallidus.
The basal ganglia have subdivisions that exchange information with different parts of the cerebral cortex. It has long been known that damage to the basal ganglia impairs movement (as in conditions like Parkinson’s disease and Huntington’s disease). The basal ganglia are critical for learning and remembering (as opposed to learning factual information or remembering specific events). They are also important for attention, language, planning and other cognitive functions.
What is the nucleus basalis?
It is part of the basal forebrain. It receives input from the hypothalamus and basal ganglia and sends axons that release acetylcholine to widespread areas in the cerebral cortex. The nucleus basalis is a key part of the brain’s system for arousal, wakefulness, and attention.
Patients with Parkinson’s and Alzheimer’s disease have impairments of attention and intellect because of inactivity or deterioration of their nucleus basalis.
Describe the hippocampus.
It is a large structure between the thalamus and the cerebral cortex, mostly toward the posterior of the forebrain. The hippocampus is critical for storing certain kinds of memories, especially memories for individual events. People with hippocampus damage have trouble storing new memories, but they do not lose all the memories they had before the damage.
What is the central canal?
A fluid filled channel in the centre of the spinal cord
What are the ventricles?
four fluid filled cavities within the brain. Each of the hemispheres contain one of the 2 large lateral ventricles. Towards their posterior they connect to the third ventricle, positioned at the midline, separating the left thalamus from the right thalamus. The third ventricle connects to the fourth ventricle in the centre of the medulla.
What is cerebrospinal fluid?
It is created inside the fourth ventricle. It is a clear fluid similar to blood plasma. CSF fills the ventricles, flowing from the lateral ventricles to the third and fourth ventricles. From the fourth ventricle, some of it flows into the central canal of the spinal cord, but more goes into the narrow spaces between the brain and the thin meninges. In one of these narrow spaces, the blood gradually absorbs the CSF.
CFS cushions the brain against mechanical shock when the had moves. It also provides buoyancy (helps to support the weight of the brain). It also provides a reservoir of hormones ad nutrition for the brain and spinal cord.
What are the meninges?
Membranes that surround the brain and spinal cord. The meninges feel pain. Meningitis is inflammation of the meninges and is painful. This pain can cause migraines.
Describe the cerebral cortex.
the cellular layers on the outer surface of the cerebral hemisphere. The cells of the cerebral cortex are gray matter and their axons extend inward are white matter.
What are the corpus callosum and the anterior commissure?
Neurons in each hemisphere communicate with neurons in the corresponding part of the hemisphere trough 2 bundles of axons called the corpus callosum and the anterior commissure.
What happens to the size of the mid and hind brain as the forebrain increases?
The hind and midbrains decrease in size.The cerebellum size remains a constant percentage of the brain size.
Describe the Occipital Lobe.
It is located at the posterior (caudal) end of the cortex. It is the main target of visual information.
The posterior pole of the occipital lobe is known as the primary visual cortex or striate cortex. Destruction of any part causes cortical blindness. eg. extensive damage in the right hemisphere causes blindness in the left visual field. The eyes are normal but no conscious visual perception and no visual imagery (not even dreams).
Describe the Parietal Lobe.
This is located between the occipital lobe and the central sulcus. It includes the postcentral gyrus (primary somatosensory cortex). The lobe uses the postcentral gyrus to help it to monitor all the info about eye, head, and body positions and passes it on to brain areas that control movement.
The lobe is essential for spatial info and numerical info.
What is the central sulcus?
the deepest grooves in the surface of the cortex.
What is the postcentral gyrus?
Also known as the primary somatosensory cortex. This area is just posterior to the central sulcus. It receives sensations from touch receptors, muscle stretch receptors and joint receptors.
The postcentral gyrus includes four bands of cells parallel to the central sulcus. Separate areas along each band receive simultaneous information from different parts of the body. 2 bands receive mostly light touch info, 1 receives deep pressure info and 1 receives a combination. In effect it represents the body four times.
It helps to interpret visual and auditory info. Eg. If you see something your brain needs to know which direction your eyes turned, the position of your head, the tilt of your body before it can determine the location of whatever you see.
Describe the Temporal Lobe.
It is the primary cortical target for auditory information. The left temporal lobe is essential for understanding spoken language. The temporal lobe also contributes to complex aspects of vision, including perception of movement ad recognition of faces. A tumour in the temporal lobe may give rise to elaborate auditory or visual hallucinations. When psychiatric patients report hallucinations, brain scans detect extensive activity in the temporal lobes. The temporal lobes are also important for emotional and motivational behaviours. Temporal lobe damage can lead to a set of behaviours known as the Kluver-Bucy syndrome.
What is the Kluver-Bucy syndrome?
Damage to the Temporal Lobes can lead to a set of behaviours known as Kluver-Bucy syndrome. It can include a lack of fear and anxieties However, interpreting the behaviour may be difficult (is it an emotional or cognitive change?)
What is the Frontal Lobe?
It contains the primary motor cortex and the prefrontal cortex. It extends from the central sulcus to the anterior limit of the brain. The posterior portion of the frontal lobe, just anterior to the central sulcus is the precentral gyrus (primary motor cortex). The most anterior position of the frontal lobe is the prefrontal cortex. In general the larger the cerebral cortex, the larger the percentage of the prefrontal cortex. The dendrites in the prefrontal cortex have up to 16 as many dendritic spines as neurons in other parts of the brain, therefore it integrates an enormous amount of information.
Describe the precentral gyrus.
It is also called the primary motor cortex and is located in the frontal lobe. It is specialised for the control of fine movements,like moving one finger at a time. Separate areas are responsible for different parts of the body, mostly on the contralateral side with slight control of the ipsilateral side. Note the map is only an approximation (there is no one to one relationship between brain locations and specific muscles).
What is a prefrontal lobotomy?
surgical disconnection of the prefrontal cortex from the rest of the brain. It caused people to lose their social inhibitions, ignore the rules of polite, civilised conduct.
Describe the prefrontal cortex.
It is a complex structure. A major function is working memory. People with damage to the prefrontal cortex have trouble on the delayed response task. It is also important for making decisions and planning movements, especially for behaviours that depend on the context. People with prefrontal damage often fail to adjust to their context (eg. answer someone elses phone)
What is the binding problem?
The question of how various brain areas produce a perception of a single object. Binding depends on perceiving two or more aspects of a stimulus as coming from approximately the same area.
What is the reticular formation?
A structure that extends from the medulla into the forebrain. It controls areas o the spinal cord and selectively increases arousal and attention in various forebrain areas
What are the categories that most research methods fall into?
- Examine the effects of brain damage.
- Examine the effects of stimulating a brain area
- Record brain activity during behaviour
- Correlate brain anatomy with behaviour
Why use animals?
Few humans have damage confined to just one brain area, and no two people have exactly the same damage
What is an ablation?
It is the removal of a brain area, generally with a surgical knife.
What are lesions?
If surgical removal of part of the brain is difficult then they will damage a structure of the brain. They often use a stereotaxic instrument.
What is a stereotaxic instrument?
They will use this to damage the brain if they need to reach an internal area of the brain. It is a devise for the precise placement of electrodes in the brain.
How do researchers create a lesion?
By consulting a stereotaxic atlas (map) of some species’ brain, a researcher aims an electrode at the desired position relative to certain landmarks on the skull. The researcher anaesthetises an animal, drills a hole in the skull, inserts the electrode, lowers it to the target and passes an electrical current, just sufficient to damage that area.
After the death of the animal, someone takes slices of its brain, applies stains, and verifies the actual location of the damage.
How do they prove the deficit rather than the procedure caused the behavioural changes?
The research produces a sham lesion in a control group using the same procedure.
What is transcranial magnetic stimulation?
The application of an intense magnetic field to a portion of the scalp, temporarily inactivated neurons below the the magnet. Thus turning the brain area on, then off, the back on again
What is the gene knock out approach?
To use biochemical methods to direct a mutation to a particular gene that is important for certain types of cells, transmitters or receptors.
What is a problem with trying to link an animals brain damage with its change in behaviour?
It is hard to know what caused the change. Did it stop eating because it lost hunger? Lost its ability to taste food? Lost its ability to find food? Etc.
What is brain stimulation and what are its limitations?
A new technique called optogenetics enables researchers to turn on activity in targeted neurons by a device that shines a laser light within the brain. The insertation of electrodes and transcranial magnetic stimulation are other ways to turn on neurons.
A limitation is that complex behaviours and experiences depend on activity across many brain areas, not just one. So stimulation can produce artificial responses.
Studies of human brains almost always use noninvasive methods. Provide some examples.
Electroencephalograph (EEG), magnetoencephalograph (MEG), positron emission tomography (PET), functional magnetic resonance imaging (fMRI)
What is an electroencephalograph (EEG)?
A device that records electrical activity of the brain through electrodes attached to the scalp. The electrodes measure the average activity at any moment of a population of cells under the electrode. It can record spontaneous brain activity or activity in response to a stimulation .
What is evoked potentials or evoked responses?
The activity measured by an EEG in response to a stimulus. These evoked potentials sometimes reveal information that self report do not.
What is a magnetoencephalograph (MEG)?
It is similar to an EEG but instead of measuring electrical activity, it measures the faint magnetic fields generated by the brain activity. It identifies the approximate location of activity to within a cemetery. However, it has excellent temporal resolution, showing changes quickly. Using the MEG researchers can identify the times at which various brain areas respond and thereby trace a wave of brain activity from its point of origin to all the other areas that process it.
What is a positron emission tomography (PET)?
A person is injected with glucose or some other chemicals containing radioactive atom. When the radioactive atoms decay
it releases a positron and emits gamma rays. The areas showing the most radioactivity are the ones with the most blood flow and therefore presumably the most brain activity. The process is expensive and it exposes the brain to radioactivity so it has largely been replaced by fMRI.
What is a functional magnetic resonance imaging (fMRI)?
An MRI scan records the energy released by water molecules after removal of a magnetic field.
The fMRI is based on hemoglobin (the blood protein that binds oxygen) instead of water. When a brain area becomes more active, first, blood vessels dilate to allow more blood flow to the area, second, as the brain uses oxygen, the percentage of hemoglobin without oxygen increased. The fMRI scans both of these processes by detecting hemoglobin with and without oxygen.
An fMRI while you were reading would mean nothing without a comparison to something else. Researchers would therefore always give you a comparison task. Interpreting fMRI results is a complex task. Because we have to be careful about equating one area with one function.
What is phrenology?
A process of relating skull anatomy to behaviour. A problem with this is that skull shape has little relationship to brain anatomy. Today researchers use CAT scans to examine the brain anatomy.
What is a CAT scan?
Computerised axial tomography. A physician injects dye into the blood and then places a person’s head into a scanner. X rays are passed through they head. The CT scanner is rotated slowly until a measurement has been taken at each angle over 180degrees. From the measurements, a computer constructs images of the brain. These help to detect tumours and other structural abnormalities.
What is a magnetic resonance imaging (MRI)?
An MRI device applies a powerful magnetic field to align all the axes of rotation and then tilts them with a brief radio frequency field. When the radio frequency field is turned off , the atomic nuclei release electromagnetic energy as they relax and return to their original axis. By measuring that energy, MRI devices form an image of the brain.
One drawback is that the person must lie motionless in a conning, noisy apparatus.
What is the relationship between brain size and intelligence?
Humans do not have the largest brains. Humans do not have the largest brain to body ratio. A further problem is a clear definition for animal intelligence. No test can compare elephants, and chimps.
Most studies do find a moderate positive correlation between brain size and intelligence. Presumably certain brain areas are more important than others for intelligence. But the different studies can not agree on the identified areas. One problem is that a give task may a ticket different areas in different people simply because they approach the task in different ways.
How do male and female brains compare?
Men on average have larger brains than women but equal IQ. Women average more and deeper sulcus on the surface of the cortex, especially in the frontal and parietal areas. Consequently, the surface area of the cortex is almost equal for men and women. Because the surface is lined with neurons (gray matter) the sexes have about the same number of neurons, despite differences in brain volume. However, intelligence does not depend on size or number of grey matter.
Therefore men’s and women ‘s brains are different structurally but can accomplish the same thing.
Men have more white matter. They are about equal in grey matter.
