Chapter 4 - Anatomy Of The nervous System

Question 1

What is the central nervous system (CNS)?

Answer 1

The brain and the spinal cord

Question 2

What is the peripheral nervous system (PNS)?

Answer 2

Connects the brain and spinal cord to the rest of the body.

Question 3

What is the somatic nervous system?

Answer 3

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.

Question 4

What is the autonomic nervous system?

Answer 4

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.

Question 5

What is dorsal?

Answer 5

The top of the brain for a 4 legged animal. For humans it is towards the back.

Question 6

What is ventral?

Answer 6

In a 4 legged animal it is the bottom of the brain but in a human it is towards the stomach

Question 7

What is anterior?

Answer 7

Toward the front end

Question 8

What is posterior?

Answer 8

Toward the rear

Question 9

What is superior?

Answer 9

Above another part

Question 10

What is inferior?

Answer 10

Below another part

Question 11

What is lateral?

Answer 11

Towards the side, away from the midline

Question 12

What is medial?

Answer 12

Toward the midline, away from the side

Question 13

What is proximal?

Answer 13

Located close to the point of origin or attachment

Question 14

What is distal?

Answer 14

Located more distant from the point of origin or attachment

Question 15

What is ipsilateral?

Answer 15

On the same side of the body

Question 16

What is contralateral?

Answer 16

On the opposite side of the body

Question 17

What are the 3 main ways in which to cut the brain?

Answer 17

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)

Question 18

What is a fissure?

Answer 18

A long, deep sulcus.

Question 19

What is sulcus?

Answer 19

A fold or groove that separates one gurus from another

Question 20

What is a gyrus?

Answer 20

a protuberance on the surface of the brain

Question 21

What is a ganglion?

Answer 21

A cluster of neuron cell bodies, usually outside the CNS

Question 22

What is a nucleus?

Answer 22

A cluster of neuron cell bodies within the CNS

Question 23

What is a nerve?

Answer 23

A set of axons in the periphery, either from the CNS to a muscle or gland or from a sensory organ to the CNS

Question 24

What is a tract ?

Answer 24

A set of axons within the CNS, also known as a projection.

Question 25

What is a column?

Answer 25

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.

Question 26

What is a lamina?

Answer 26

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.

Question 27

What is the spinal cord?

Answer 27

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.

Question 28

What is the Bell-Magendie law?

Answer 28

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.

Question 29

what is a dorsal root ganglia?

Answer 29

The cell bodies of the sensory neurons are in clusters of neurons outside the spinal cord.

Question 30

What is inside the spinal cord?

Answer 30

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.

Question 31

Why are the segments of the spinal cord important?

Answer 31

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.

Question 32

What is the autonomic nervous system?

Answer 32

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

Question 33

What is the sympathetic nervous system responsible for?

Answer 33

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.

Question 34

What receives only sympathetic input?

Answer 34

The sweat glands, the adrenal glands, the muscles that constrict blood vessels, and the muscles that erect the hairs of the skin.

Question 35

What does the parasympathetic nervous system do?

Answer 35

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.

Question 36

Why is the parasympathetic nervous system also known as the craniosacral system?

Answer 36

Because it consists of the cranial nerves and nerves from the sacral spinal cord.

Question 37

Describe the ganglia of the parasympathetic nervous system.

Answer 37

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.

Question 38

What neurotransmitters do the parasympathetic and sympathetic nervous systems use?

Answer 38

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.

Question 39

Name the 6 segments of the spinal cord.

Answer 39

Cranial nerves (12 pairs), cervical nerves (8 pairs), thoracic nerves (12 pairs), lumbar nerves (5 pairs), sacral nerves (5 pairs), coccygeal nerves (1 pair).

Question 40

What is the hindbrain?

Answer 40

The posterior part of the brain consisting of the medulla, the pons, and the cerebellum. These are all part of the brain stem.

Question 41

What is the brain stem?

Answer 41

the medulla, the pons, the cerebellum and certain central structures of the forebrain (thalamus, superior colliculus, inferior colliculus, tectum, tegmentum, pineal gland)

Question 42

describe the medulla oblongata.

Answer 42

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.

Question 43

Describe the cranial nerves.

Answer 43

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.

Question 44

Describe the pons.

Answer 44

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.

Question 45

What is the raphe system?

Answer 45

It sends axons to much of the forebrain, modifying the brain’s readiness to respond to stimuli

Question 46

Describe the cerebellum

Answer 46

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).

Question 47

Describe the midbrain.

Answer 47

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

Question 48

Describe the forebrain

Answer 48

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.

Question 49

Describe the thalamus.

Answer 49

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

Question 50

What are the parts of the limbic system?

Answer 50

Cingulate gyrus, thalamus, hypothalamus, mamillary body, hippocampus, amygdala, olfactory bulb

Question 51

Describe the hypothalamus

Answer 51

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.

Question 52

What is the pituitary gland?

Answer 52

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.

Question 53

Describe the basal ganglia.

Answer 53

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.

Question 54

What is the nucleus basalis?

Answer 54

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.

Question 55

Describe the hippocampus.

Answer 55

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.

Question 56

What is the central canal?

Answer 56

A fluid filled channel in the centre of the spinal cord

Question 57

What are the ventricles?

Answer 57

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.

Question 58

What is cerebrospinal fluid?

Answer 58

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.

Question 59

What are the meninges?

Answer 59

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.

Question 60

Describe the cerebral cortex.

Answer 60

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.

Question 61

What are the corpus callosum and the anterior commissure?

Answer 61

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.

Question 62

What happens to the size of the mid and hind brain as the forebrain increases?

Answer 62

The hind and midbrains decrease in size.The cerebellum size remains a constant percentage of the brain size.

Question 63

Describe the Occipital Lobe.

Answer 63

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).

Question 64

Describe the Parietal Lobe.

Answer 64

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.

Question 65

What is the central sulcus?

Answer 65

the deepest grooves in the surface of the cortex.

Question 66

What is the postcentral gyrus?

Answer 66

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.

Question 67

Describe the Temporal Lobe.

Answer 67

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.

Question 68

What is the Kluver-Bucy syndrome?

Answer 68

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?)

Question 69

What is the Frontal Lobe?

Answer 69

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.

Question 70

Describe the precentral gyrus.

Answer 70

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).

Question 71

What is a prefrontal lobotomy?

Answer 71

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.

Question 72

Describe the prefrontal cortex.

Answer 72

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)

Question 73

What is the binding problem?

Answer 73

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.

Question 74

What is the reticular formation?

Answer 74

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

Question 75

What are the categories that most research methods fall into?

Answer 75

1. Examine the effects of brain damage.
2. Examine the effects of stimulating a brain area
3. Record brain activity during behaviour
4. Correlate brain anatomy with behaviour

Question 76

Why use animals?

Answer 76

Few humans have damage confined to just one brain area, and no two people have exactly the same damage

Question 77

What is an ablation?

Answer 77

It is the removal of a brain area, generally with a surgical knife.

Question 78

What are lesions?

Answer 78

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.

Question 79

What is a stereotaxic instrument?

Answer 79

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.

Question 80

How do researchers create a lesion?

Answer 80

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.

Question 81

How do they prove the deficit rather than the procedure caused the behavioural changes?

Answer 81

The research produces a sham lesion in a control group using the same procedure.

Question 82

What is transcranial magnetic stimulation?

Answer 82

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

Question 83

What is the gene knock out approach?

Answer 83

To use biochemical methods to direct a mutation to a particular gene that is important for certain types of cells, transmitters or receptors.

Question 84

What is a problem with trying to link an animals brain damage with its change in behaviour?

Answer 84

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.

Question 85

What is brain stimulation and what are its limitations?

Answer 85

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.

Question 86

Studies of human brains almost always use noninvasive methods. Provide some examples.

Answer 86

Electroencephalograph (EEG), magnetoencephalograph (MEG), positron emission tomography (PET), functional magnetic resonance imaging (fMRI)

Question 87

What is an electroencephalograph (EEG)?

Answer 87

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 .

Question 88

What is evoked potentials or evoked responses?

Answer 88

The activity measured by an EEG in response to a stimulus. These evoked potentials sometimes reveal information that self report do not.

Question 89

What is a magnetoencephalograph (MEG)?

Answer 89

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.

Question 90

What is a positron emission tomography (PET)?

Answer 90

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.

Question 91

What is a functional magnetic resonance imaging (fMRI)?

Answer 91

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.

Question 92

What is phrenology?

Answer 92

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.

Question 93

What is a CAT scan?

Answer 93

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.

Question 94

What is a magnetic resonance imaging (MRI)?

Answer 94

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.

Question 95

What is the relationship between brain size and intelligence?

Answer 95

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.

Question 96

How do male and female brains compare?

Answer 96

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.